Chapter # 1          INTRODUCTION TO BIOLOGY

Q.1. Tick the correct answer.                                
1. Members of the same species living in the same place at the same time make a?
(a) Habitat (b) Biosphere (c) Community (d) Population
2. If a scientist is studying the methods of inserting human insulin gene in bacteria, which branch of biology may this be?
(a) Anatomy (b) Physiology (c) Biotechnology (d) Pharmacology
3. Which one will be the correct sequency of the levels of organization of life?
(a) Cell, organelle, molecule, organ tissue, organ system (b) Molecule, tissue, organelle, cell, organ system, organ (c) Molecule organelle, cell, tissue, organ, organ system, (d) Organ system, organ, tissue cell, molecule, organelle, individual
4. Which of these major bioelements is in the highest percentage in protoplasm?
(a) Carbon (b) Hydrogen (c) Oxygen (d) Nitrogen
5. Which of the following group includes organisms all of which are absorptive in their nutrition?
(a) Prostists (b) Animals (c) Bacteria (d) Fung
6. Similar cells organized into groups and performing same functions, are known as?
(a) Organelle (b) Tissue (c) Organ (d) Organ system
6. Which of these tissues also makes the glandular tissue in animals?
(a) Epithelial tissue (b) Muscular tissue (c) Connective tissue (d) Nervous tissue
8. The level of organization that is less definite in plants is?
(a) Tissue level (b) Organ level (c) Organ system level (d) Individual level
9. What is true about volvox?
(a) Unicellular prokaryotic (b) Unicellular eukaryotic (c) Colonial eukaryotic (d) Multicellular eukaryotic
10. When we study the feeding relations among different animals species of a forest, at what level of organization we are studying?
(a) Individual (b) Population (c) Community (d) Biosphere



Q2. Write the answers of the following short question.

  1. Define biotechnology?

Biotechnology is a branch of biology, which deals with practical application of living organisms to make substances, necessary for the welfare of mankind.

  1. What do you mean by horticulture and how it is related to agriculture?

Dealing with the art of gardening is called horticulture. Like an agriculturist, a horticulturist keep on working to develop better varieties of ornamental and fruit plants. Better varieties of fruits increase the better yield of agriculture.

Q3. Write the detailed answers of the following questions.

  1. Define the following terms.
  2. Science
  3. Life

Ans. Science:

In order to understand the principles of nature which are beautifully ordered and coordinated in its activities, observations are made, experiments are done and logical conclusions are drawn. Such studies are called science.

In ancient times, the scientific information was not classified into different branches, as it exists today. All the scientific information was included under on head i.e. science. With the passage of scientific information increased many folds and this enormous scientific knowledge was then classified into different branched like, biology, physics, chemistry, mathematics, etc.


It has always been a difficult task to define life. Biologists define life as a set of characteristics that distinguish living things from non-livings. All of these characteristics are found in each living thing, which is called an “organism”.

  1. Define biology and discuss its major divisions.

Ans. Biology:

The word “biology” has been derived from two Greek words: “Bios” meaning life. “Logos” meaning “thoughts or reasoning”.

Biology is the scientific study of life or living organisms. Through this study, the scientists (biologists) do their best to understand, explain, integrate describe the world of living things. Biology is the sum of human knowledge about life.

In the course of biology we will study.

  1. How man has thought about living things.
  2. How to understand and appreciate nature.
  • The structure, functions and related aspects of living organisms.
  1. Information and remedies to human problems regarding health, food, environment etc.

We are familiar with the division of living organisms into different groups.


The unicellular organisms that do not have distinct nucleus are grouped as prokaryotes for example bacteria.


The unicellular or simple multicellular organisms with distinct nuclei are called protests e.g. euglena, paramecium, green algae etc.


Fungi e.g. mushrooms are multicellular, heterotrophic and absorptive in their mode of nutrition.


Plants e.g. mustard are multicellular autotrophic organisms that develop from embryos.


Animals e.g. frog are multicellular heterotrophic organisms that ingest food.

  1. Define biology and discuss its major divisions.

Ans. Major Divisions of Biology:

This division of biology deals with the study of microorganisms such as bacteria etc.


This division of biology deals with the study of animals.


This division of biology deals with the study of plants.


This division of biology deals with the study of microorganisms such as bacteria etc.

  1. Write down the braches of biology and the studies theses deal with.

Ans. Branches of Biology:

It becomes necessary to divide biology into a number of branches to handle volumes of information. Now it is convenient to study all the aspects of life. Some of these branches are define here.


This branch deals with the study of the structures of living organisms. The study of internal structure is called anatomy.


This microscopic study of tissues is called histology.

Cell biology:

The study of the structures and functions of cells and cell organelles is called cell biology. This branch also deals with the study of cell division.


This branch deals with the study of the functions of different parts of living organisms.

Molecular biology (biochemistry):

This branch deals with the study of the molecules of life, water, proteins, carbohydrates, lipids and nucleic acids. The study of the biochemical reactions occurring in organisms is also included in this branch.


It is the study of inheritance. Inheritance means the transmission of characters from one generation to the other. Genetics provides important tools in the investigation of the structure and functions are genes.


It is the study of the development of a new individual from a fertilized egg. Embryologists study the cell growth. Differentiation, and morphogenesis (the process that gives rise to tissues and organs).


It is the study of the naming and classification of organisms into groups and subgroups.


It is the study of fossils, which are the remains of extinct organisms. Paleontologists study the age the structure of fossils and on this basis study the process of evolution.

Environmental biology:

It deals with the study of the interactions that exist between the organisms and their environment. All living and non-living factors that surround an organism, constitute its environment. Communal life means interactions within community, while community is defined as organisms of all species living in a particular habitat at a particular time. Human population growth, infectious diseases, addictive drugs, and environmental pollution are the major biological issues today.


This branch deals with the study of parasites. Parasites are the organisms that take food and shelter from living hosts and, in return harm their (hosts) lives. The structure, habitats, mode of transmission, life histories and host-parasite relationships are studies in parasitology.

Socio biology:

This branch deals with the study of social behavior and communal life of living organisms.


The term biotechnology is only used when microorganisms, plants or animals are used to produce something other than food. So use of farm animals and crops from milk, meat, eggs and cereals is not included in biotechnology. Biotechnology means the practical application of the knowledge about living organisms to carry out processes, which make substances for the welfare of mankind e.g. disinfection and preservation of food, preparation of insulin, biogas etc.


It is the study of the immune system of animals, which defends the body against invading microbes.


It is the study of insects. Entomologists study the general characteristics and life cycles of beneficial and harmful insects.


It is the study of drugs and their effects on the systems of human body.

  1. Give points to advocates that biology is linked with physics, chemistry, mathematics, geography and economics.

Ans. Relationship of biology to other sciences:

The interrelationship among different branches of science cannot be denied. Biology includes information on various aspects of living things but this information relate to the other branches of science as well. Each branch of science has relationships with all other branches.

For example, when studying the process of movement in animals, the biologists have to refer to the laws of motion in physics. This forms the basis of interdisciplinary sciences.


It deals with the study of the principles of physics, which are applicable to biological phenomena. For example there is a similarity between the working principles of lever in physics and limbs of animals in biology.


It deals with the study of the chemistry of different compounds and processes occurring in living organisms. For example the study of basic metabolisms of photosynthesis and reparation involves the knowledge of chemistry.


It deals with the study of biological processes using mathematical techniques and tools. It has both practical and theoretical applications in biological research. For example to analyze the data gathered after experimental work, biologists have to apply the rules of mathematics.


It studies the occurrence and distribution of different species of living organisms in different geographical regions of the world. It applies the knowledge of the characteristics of particular geographical regions to determine the characteristics of living organisms found there.

Bio economics:

It studies the organisms from economical point of view. It includes the study of the cost effectiveness and validity of biological projects. For example the cost value and profit value of the yield of wheat can be calculated through bio economics and benefits or losses can be determined.

  1. Write a descriptive not on the careers in biology.

Ans. Careers in Biology:

An accurate and modern knowledge of biology, would promote a comprehensive of both science and scientific research project, which would benefit the learners in diverse list of careers.

The following are the careers that a student of biology can plan to adopt.


This profession of medicine deals with the diagnosis and treatment of diseases in human. In surgery the parts of the body may be repaired. Replaced or removed, for example the removal stones through renal surgery, transplantation of kidney, live etc. Both these professions are studied in the same basic course (MBBS) and then students go for specializations.


Fisheries is the professional study of fish production. There are departments in Pakistan where professionals of fisheries are employed. They serve for enhancing the quality and quantity of fish reproduction. In Pakistan, this profession can be adopted after bachelor or masters level study of zoology and fisheries.


This profession deals with the food crops and animals which are the source of food. An agriculturist works for the betterment of crops like wheat, rice, corn etc and animals from which we get food. In Pakistan there are many universities which offer professional courses on agriculture after the higher secondary education in biology.

Animal husbandry:

It is the professional study of the diagnosis and treatment of diseases of the livestock. The livestock includes all the domestic animals. Professional courses in animal husbandry can be adopted after the higher secondary education in biology.


This profession includes the art of gardening. A horticulturist works for the betterment of existing varieties and for the production of new varieties of ornamental plants and fruit plants. Biology students can adopt this profession after their higher secondary education.


In this profession different types of farm are developed and maintained. For example ion some farms animal breeding technologies are used for production of animals which are better protein and milk source. In poultry farms chicken and eggs are produced. Similarly in fruit farms, professional course of agriculture, animal husbandry or fisheries etc can adopt this profession.


In forestry, professionals look after natural forests and advise to the government for planning and growing artificial forests. Many universities offer professional courses in forestry after the higher secondary education in biology or after bachelor level study of zoology and botany.


It is the latest profession in the field of biology. Biotechnologies study and work for the production of useful products through microorganisms. Universities offer courses in biotechnology after the higher secondary education in biology and after the bachelor level studies of botany or zoology.

  1. Giving example through verses, discuss the quranic instructions to reveal the study of life?

Ans. Quranic instruction:

At many places in Holy Quran, Allah hints the origin and characteristics of living organisms. In the save verses human beings have been instructed to expose the unknown aspects of life, after growing the hints, here are few examples of such guidelines.

“We made every living thing from water”.(Surah: Ambia, verse: 30)

We know that water makes the 80-90% of the composition of protoplasm of all living things. The above verse hints at the common origin of all living things in water. As Allah had ordered human beings to think at the hints given by him, we should study living things so that the mysteries of their origin can be revealed.

“He made man from clay like the potter”. (Surah: Rehman, verse 14)

When we think at the hints given in both these verses, we find the events that occurred in the creation of human beings. Allah also hints at the method of the development of animals including beings.

“Then fashioned we the drop a clot, then fashioned we the clot is the little lump, then fashioned we the little lump bones, the clotted the bones with flesh”. (Surah: Al Mominoon, verse 14)

          Now here is a verse that describes the common origin and modification of organisms. This verse also supports the modern concepts of classification.

“Allah hath created every animal from water, then some of them creep up over their bellies, others walk on two legs, and others on four. Allah creates what he pleases”. (Surah: Al Noor, verse 45)

Quran hints not only at the origin and development of life but also at many characteristics of living organisms. Scientists reveal such mechanisms.

  1. Give an account of few Muslim scientists who are famous for biology?

Ans. Muslim Scientists:

Muslim scientists have made great contributions to the study of the biology. Three of them are discussed here.

Jabir Bin Hayyan:

  • Time period:

(712   815)

  • Birth:

He was born in Iran and practiced medicine in Iraq.

  • Contribution:

He introduced experimental investigation in chemistry Jabir bin Hayyan wrote a number of books on plant and animals. His two most famous books are “Al- Nabatat” and “Al-Haywan”.

Abdul Malik Asmai:

  • Time period:

(740   828)

  • Contribution:

He is considered the first Muslim scientist who studied animals in detail.

  • Books:

His famous writing include “Al-Abil” (camel). “Al-Khail” (horse) “Al-Wahoosh” (Animal), and “Kalq al-ansan”.

Bu Ali Sina:

  • Time period:

(980   1037)

  • Contribution:

He is honored as the founder of medicine and called as Avicenna in the west. He was physician, philosopher, astronomer and poet.

  • Books:

One of his books “Al-Qanun-fl-al-Tib” is known as the canon of medicine in west.

  1. Describe the levels of organization of life?

Ans. The study of biological organization of different levels helps biologists understand different phenomena of life. Biological organization goes from simpler to complex levels i.e. from subatomic level to biosphere.

Subatomic particles make atoms and atoms make molecules. Different molecules of life make organelles and different organelles assemble together to from the simplest living unit i.e. the cell. Cells are organized in the form of tissues and different coordinating tissues make an organ. Organs performing relative functions make organ system and different organ systems make a complete individual. Individuals of the same species live together and make a population. Populations of different species living in the same habitat constitute a community. The part of the earth inhabited by different organisms or communities is known as biosphere.

The levels of organization:

Description of all these levels is as under.

Subatomic and atomic level:

All types of matter are made up of elements and there are about 92 kinds of elements, found in nature. Each element is made up of a single kind of atom (‘a’: not, ‘tom’: cut). These atoms are actually the structures formed by by many subatomic particles. The most stable subatomic particles are electrons, protons and neutrons. Each of these is found in definite number, in a specific atom. Protons and neutrons are located inside nucleus of atom while electrons orbit in energy levels (electron shells) around the nucleus. The number of electrons in the outermost shell determines the manner in which atoms react with each other.

Out of the 92 kinds of elements that occur in nature, 16 are called bio elements. These take part in making the body mass of a living organism.

Out of these bio elements only six (O, C, H, N, Ca, & P) make 99% of the total mass. Other ten (K, S, Cl, Na, Mg, Fe, Cu, MN, Zn, & I) collectively make 01% of the total mass.

Molecular level:

In organisms, bio elements usually do not occur in isolated forms. Rather, atoms of different bio elements combine through ionic or covalent bonding. The stable particle formed by the bonding between different elements is called as molecule. A molecule is the smallest part of a compound that retains the properties of that compound. Bio elements share their atoms in making biomolecules or molecules of life.

Biological molecules:

An organism is formed by enormous number of biomolecules of hundreds of different types. These molecules are the building material and are themselves constructed in great variety and complexity due to specific bonding arrangements.

Biomolecules may be classified as:

  1. Micro molecules
  2. Macromolecules

Micro molecules:

Micro molecules are with low molecular weight e.g. glucose, amino acids, fatty acids etc.


Macromolecules are with high molecular weights e.g. starch, proteins, lipids, etc.

Organisms and cell level:

An enormous number of biomolecules become associated in a particular way and form organelles.

The organelles are actually sub-cellular structures and when they assemble together, cells are formed.

Each type of organelle is specialized to perform a specific function. For example; mitochondria are specialized for cellular respiration and ribosomes are specialized from protein synthesis. All functions of the cell are accomplished by these specialized structures. It is an example of the division of labor within the cell.


Have only limited number and types of organelles in their cells. They are made up of simple cells which lakh membrane bounded organelles e.g. mitochondria, Golgi complex.


Have large number and types of organelles in their cells. They are made up of complex cells which have membrane bounded organelles.

In the case of bacteria and most protests, the entire organism consists of a single cell. They are called unicellular organisms.

In the case of most fungi, animals and plants, the organism consists of up to trillions of cells. They are called multicellular organisms.

Tissue level:

In multicellular organisms, similar cells (performing similar functions) are organized into groups, called tissues.

A tissue as a group of similar cells specialized for the performance of a common function. Each cells in a tissue carries on its own life processes (like cellular respiration, protein synthesis), but it also carries on some special processes related to the function of the tissue.

Plant tissues:

Plant tissues are divided into different type e.g. epidermal tissues, ground tissues.

Animal tissues:

These are also of different e.g. nervous tissue and muscular tissues.

Organ and organ system level:

In higher multicellular organisms, particularly in animals, more than one type of tissue having related functions are organized together and make a unit, called organ.

Different tissues of an organ perform their specific functions and these functions collectively become the function/s of that organ. For example stomach is an organ specialized for the digestion of proteins and for storing food. Two major types of tissues are organized in its structure. Epithelial (glandular) tissue secrets the gastric juice and muscular tissue performs constraints of stomach walls for grinding of food, mixing of enzymes with food and moving food to posterior end. So, two tissues perform their specific functions, which collectively become the function of stomach.

The next level of organization in multicellular organisms is the organs system level. Different organs performing related functions are organized together in the form of an organ system. In an organ system, each organ carries out its specific function and the functions of all organs appear as one process of the organ system. For example, digestive system is an organ system that carries out the process of digestion. Major organs arranged in its framework are oral cavity, stomach, small intestine, large intestine, liver, and pancreas. Table 1.1 describes the specific roles played by all these organs in the process of digestion.

The organ system level is less definite in plants as compared to animals. The complexity of organ and organ system in animals is associated with a far greater range of functions and activities than in plants.

Individual level:

Different organs (in plants) and organ systems (in animals) are organized together to form an individual/organism. In organism, various organs and organ systems are organized in such a way that all the functions, processes and activities are coordinated. The whole organism has its individually as far as its characteristics are concerned. For example; all human beings have same organs and organ systems which are organized in the same pattern. Yet they have different skin colors, heights, voice tones etc.

Such characteristics make the individually in a human being. For example, when a man is engaged in continuous and hard exercise, not only his muscles are working but also there is an increase in the rate of respiration and heartbeat. This accelerated rate of respiration and heart beat supplies more oxygen and food to the muscles which they need for continuous work. In animals, regulation of activities (co-ordination) is achieved by nervous system and hormones while in plants, co-ordination is brought about only by hormones.

Population level:

Biologists extend their studies to the population level where they study interactions among member of the same species in the same habitat. A population is defined as a group of organisms of the same species located in the same place, at the same time. For example, number of rats in a field of rice in 2002, number of students in biology class in semester 2008 etc. Similarly, human population comprises the number of human beings in a particular time.

At population level, biologist study life in a number of new parameters, which cannot be considered at individual (organism) level. For example, gene frequency, gene flow, age distribution, population density, population pressure, etc.

Community level:

A community is an assemblage of different population, interacting with one another within the same environment. A forest may be considered as a community. It includes different plant species e.g. oak trees, ash trees, grasses, bushes etc; different species of microorganisms and fungi; and different animal specials.

Communities are collections of organisms, in which population may increase and others may decrease. Usually populations change due to fluctuations in abiotic factors and changes in the size of other populations.

Some communities are complex e.g. a forest community, a pond community etc. Other communities may be simple e.g. a fallen log with various populations under it. In a simple community number and size of populations is limited so any change in biotic or abiotic factors may have drastic and long lasting effects.

Biosphere level:

The part of the earth inhabited by organism’s communities is known as biosphere. It constitutes all ecosystems (areas where living organisms interact with the non-living components of the environment) and is also called the zone of life on earth.

Q10. How would you distinguish the biomolecules from other molecules? What is the criterion for classifying a biomolecules as micro molecules or macromolecules?

Ans. An organism is formed by enormous number of biomolecules of hundreds of different types. These molecules are the building material and are themselves constructed in great variety and complexity due to specific bonding arrangements.

Biomolecules may be classified as:

  1. Micro molecules
  2. Macromolecules

Micro molecules:

Micro molecules are with low molecular weight e.g. glucose, amino acids, fatty acids etc.


Macromolecules are with high molecular weights e.g. starch, proteins, lipids, etc.

  1. Describe in detail the cellular organization and division of labor in organisms?

Ans. Cellular organization:

In living organisms the cells organize in three ways to make the bodies of organisms.

  1. Some cells make unicellular organization in unicellular organisms, which are made up of one cell only. Such as Amoeba, Paramecium and Euglena, etc.
  2. Some cells make colonial organization in colonial organisms. In colonial type of cellular organization many unicellular organisms live together but do not have any division of labor among them. Each unicellular organism in a colony lives its own life and does not depend on other cells for its vital requirements. Volvox is a green alga found in water that shows colonial organization. Hundreds of Volvox cells make a colony.

Sometime a Volvox colony consists of daughter colonies. Each cell of the colony has two flagella at the anterior end, which is directed towards



the surface of the colony. The colony moves in water by the combined action of the flagella of all the cells.

  1. Cells make multicellular organizations in multicellular organisms. In multicellular organization cells are organized in the form of tissues, organs and organ systems. They show division of labor.

Mustard plant:

Mustard plane is shown in winter and it produces seeds at the end of winter. The plant body is used as vegetables and its seeds are used for extracting oil. The organs of the body can be divided into two groups on the basis of their functions. Root, stem, branches and leaves are the vegetable organs, which do not take part in the sexual reproduction of the plant. Flowers are the reproductive parts of the plant because they take part in sexual reproduction and produce fruits and seeds.


Frog also shows the multicellular organization. The body is made of organ systems and each organ system consists of related organs. All the organs are made of specific tissues (epithelial, glandular, muscular, nervous etc). Some organs and organ systems of frog have been describes in the practical activity given next.


Q.1. Tick the correct answer.                                
1. Which one of the following is a correct sequence in biological method?
(a) Observation, hypothesis, law, theory (b) Hypothesis, observations, deduction, experimentation (c) Observations, hypothesis, deduction, experimentation (d) Law, theory, deduction, observations
2. Which one of these is not a characteristic of a hypothesis?
(a) Must be consistent with all available data (b) Must be testable (c) Must be correct (d) Must make predictions
3. At which point is a biologist most likely to use deductive reasoning?
(a) While taking observations (b) During hypothesis formulation (c) During data organization (d) None of the above
4. A hypothesis must be testable to be scientifically valid. Being testable means that?
(a) Some observation could prove the hypothesis  incorrect (b) Only a controlled experiment can indicate whether the hypothesis is correct or incorrect (c) The hypothesis has been proven wrong (d) There must be several options in the hypothesis is to choose from, one of which is correct
5. What would be the best experimental design for testing a hypothesis that bean plants required sodium?
(a) Measure the amount of sodium in a few bean plants (b) Grow bean plants with and without sodium (c) Look for sodium in leaf tissues (d) Analyze root contents for sodium
6. A gardener sees a large snake nearby. He knows that generally snakes sting, so the gardener ran away. The gardener which of the following?
(a) Used inductive reasoning (b) Used deductive reasoning (c) Constructed a theory (d) Tested a hypothesis
6. A scientific theory has which of the following properties?
(a) It agrees with available evidence (b) It cannot be rejected (c) It has been absolutely evidence (d) It does not need to be altered in the light of new evidence
8. Experimentation is only a step of the scientific process, but it is a very important step because it always?
(a) Gives the biologist a correct result (b) Allows rejection of some alternative hyposthesis (c) Ensures that hypothesis can be confirmed with certainly (d) Give scientists a chance to work in the laboratory
9. You are testing a hypothesis, “students learn more if they drink tea before sitting for study”. Your 20 experimental students drink tea before study; you test their learning by giving question. Your 20 students of the control group should have all experimental conditions identical to the experimental group expect that;
(a) They should take tea with more milk and sugar (b) They should take tea before as well as during study (c) They should not take tea before studying (d) After taking tea, they should not sit for studying



Q2. Answer these short questions.

  1. What is meant by the word ‘malaria’?

Ans. The word ‘malaria’ is derived from two Greek words. ‘Mala’ means ‘bad’ and ‘aria’ means ‘air’ i.e. disease of bad air.

  1. Define scientific method of study?

Ans. The method from which we find solution of different problems is called scientific method of study. It includes observation, hypothesis, deduction, experiments, results, theory and principle.

  1. What is meant by deduction?

Ans. Logical conclusion drawn from a hypothesis forms deduction.

  1. What is the cause of malaria?

Ans. Plasmodium is the cause of malaria.

  1. How plasmodium enters the blood of an organism?

Ans. Plasmodium enters the blood of an organism through infected female anopheles mosquito. When this mosquito sucks the blood of a healthy person, it pours some saliva into the blood to prevent clotting in the needle. This saliva contains plasmodium.

  1. Define vector?

Ans. An organism responsible for the spread of a disease from one person to another is called vector or carrier.

  1. From which bark quinine was firstly obtained?

Ans. Quinine was obtained from the bark of Quina quina plant.

  1. Why it is said that man has always been a biologist?

Ans. Man has always been a biologist. He has to be a biologist in order to live. Early in history, he was a hunter of animals and a gatherer of fruits, seeds, roots etc. The more he knew about animals and their habitat, the more successful hunter he was. The more he knew about plants, the better he distinguished between edible from non-edible plants.

  1. Why biological methods of study are vital to the welfare of future population?

Ans. The increasing world population, coupled with the increase in the incidence of new diseases and mutations of existing disease strains, destruction of our ecological resources, and global climate change indicate that the biological method is vital to the welfare of future populations.

  1. What are the good characteristics of a hypothesis?

Ans. A hypothesis should have the following characteristics.

  1. It should be a general observations.
  2. It should be a tentative idea.
  • It should agree with available observations.
  1. It should be kept as simple as possible.
  2. It should testable and potentially falsifiable. In other words, there should be a way to shoe the hypothesis is false, a way to disprove the hypothesis.

Q3. Answer the following long questions.

  1. What do you meant by biological method of study?

Ans. Science is the systemized knowledge derived from observations and experiments carried out to determine the principles about how the nature operates.

Many scientists including chemists, biologists, ecologists and physicians all use the same scientific method to make and test new theories.

Biological method of study:

The scientific method in which biological problems are solved, is termed as biological method. It comprises the steps a biologist adopts in order to solve a biological problem.


Questions about living things have provided problems that man has investigated to aid his own survival and to satisfy his desire to know. The biological method has played an instrumental part in scientific research for almost 500 years. From Galileo’s experiment back in the 1590s to current research, the biological method has contributed to the creation of vaccines and advancements in medicine and technology. The biological method also ensures the quality of data for public use.

The increasing word population, coupled with the increase in the incidence of new diseases and mutations of existing disease strains, destruction of our ecological resources, and global climate change indicate that the biological method is vital to the welfare of future populations.

  1. Describe the steps involved in the solving a problem through biological method.

Ans. In solving a biological problem. Biologist takes following steps:

  1. Recognition of biological problem
  2. Observations
  • Hypothesis formulation
  1. Deductions
  2. Experimentation
  3. Summarization of results (create table, graphics etc)
  • Reporting the results

The details of these steps are as under:

Recognition of biological problem:

Biologists go for adopting biological method when they encounter some biological problem. A biological is a query about life that is either asked by someone or comes in biologists mind by himself.


As the first step in solving a biological problem, the biologist recalls his/her previous observations or makes new ones.

Observations are made with five senses of vision, hearing, smell, taste and touch.

Kinds of observations:

  1. Qualitative observations:

Qualitative observations are considered less accurate then quantities ones because the qualitative observations are variable and non-measurable and cannot be recorded in terms of number.

For example:

The freezing point of water is colder than the boiling. One liter of water is heavier than one liter of ethanol.

  1. Quantitative observations:

Quantitative observations are considered more accurate then qualitative ones because the quantitative observations are invariable and measureable and can be recorded in terms of number.

For example:

The freezing point of water is  and the boiling point is .

The mass of one liter water is 1000 grams while the mass of one liter ethanol is 789 grams.

Sources of observation:

Observations also include reading and studying what others have done in the past because scientific knowledge is ever-growing. Darwin not only observed and took notes during his voyage, but he also reads the works of other naturalists to form his theory of evolution.

Construction (Formulation) of Hypothesis:

Observations do not become scientific observations until they are organized and related to a question.


Biologist organizes his/her and others observations into data form and constructs a statement that may prove to be the answer of the biological problem under study. This tentative explanation of the observations is called a hypothesis. Hypothesis

Hypothesis may be defined as proposition that might be true.

Characteristics of a Good hypothesis:

A hypothesis should have the following characteristics.

  1. Hypothesis should be a general statement.
  2. Hypothesis should be a tentative idea.
  • Hypothesis should agree with available observations.
  1. Hypothesis should be kept as simple as possible.
  2. Hypothesis should testable and potentially falsifiable. In other words, there should be a way to show the hypothesis is false, a way to disprove the hypothesis.


A great deal of careful and creative thinking is necessary for the construction of a hypothesis. Biologists use reasoning to formulate a hypothesis.


The biologist draws deduction from the hypothesis.


Deductions are the logical consequences of the hypothesis. Deductions are also drawn by using inductive and deductive reasoning. Generally, in the biological method, If a particular hypothesis is true then one should expect (deduction) a certain result. This involves the use of “if-then” logic.

Biologist cannot usually check every situation where a hypothesis might apply. Let’s consider a hypothesis; “All plant cell have a nucleus.” Biologist cannot examine every living plant and every plant that has ever lived to see if this hypothesis is false. Instead, biologists generate deduction using reasoning. From the above hypothesis, a biologist can make the following deduction.

“If I examine cells from a blade of grass, then each one will have a nucleus.”


The most basic step of biological mehtodis that biologists perform experiments to see if the hypothesis are true. The deductions, which are draw from hypothesis, are subjected to rigorous testing. Through this stage, biologist learns which hypothesis are actually true from among the many that might be true. If the expected results are obtained from the tests on a hypothesis, it supports (but does not prove) the hypothesis.

The incorrect hypothesis are rejected and those which prove consistent with experimental results are accepted. An accepted hypothesis needs to be valid and useful. It makes further predictions that provide and important way to further test its validity.

Methods of experimentation:

In science when doing the experiment, it must be a controlled experiment. The scientist must contrast an “experimental group” with a “control group”. The two groups are treated exactly alike except the one variable being tested.

For example, in an experiment to test the necessity if carbon dioxide for photosynthesis, one can contract the control group (a plant with freely available carbon dioxide) with an experimental group (a plant with no carbon dioxide available. The necessity of carbon dioxide would be proved when photosynthesis occurs in the control group and does not occur in the experimental group.

Summarization of results:

The biologist gathers actual quantitative data from the experiments. Data for each of the groups are then averaged and compared statistically. To draw conclusions, the biologist also uses statistical analysis.

Reporting the results:

Biologists publish their findings in scientific journals and books, in talks at national and international meetings and in seminars at colleges and universities. Publishing of results is an essential part of the scientific method as it allows other people to verify the results or apply the knowledge to solve other problems.

  1. Describe the steps involved in biological method taking malaria as an example?

Ans. Study of Malaria:

Malaria is a common disease in many countries including in Pakistan. Malaria has killed more people than any other disease.

History of Malaria:

More than 2000 years ago, physicians were familiar with malaria. They described it as a disease of chills and fever with recurring attacks.

Naming of malaria:

Old physicians observed that the disease was more common amongst people living in low marshy areas. It was thought that the stagnant water of marshes poisoned the air and as a result of breathing in this “bad air”, people got malaria.

This belief led to the name of the disease. The word “malaria” is the combination of two Italian words:

“Mala” means “bad”“aria” means “air”

Some volunteers drank the stagnant water from the marshes. They did not develop malaria.

Discovery of quinine:

In the seventeenth century, the new world (America) was discovered. Many plants from America were sent back to Europe to be used as medicines. The bark of a tree known as Quina quina was very suitable for curing fevers. It was so beneficial that soon it was impossible to carry enough bark to Europe.

Some dishonest merchants began to substitute the bark of another tree, the cinchona which closely resembled Quina quina. This dishonesty proved much profitable for mankind. The cinchona bark was found to be excellent for treating malaria as its bark contains quinine that is effective in treating the disease.

Discovery of plasmodium:

At that time physicians treated malaria with cinchona without understanding the cause of malaria. Two hundred years later, it was found that some disease are caused by tiny living organisms. After this discovery, it also became a belief that malaria, too, might be caused by some microorganism.

In 1878 a French army physicians Laveran began to search for the “cause” of malaria. He took a small amount of blood from a malarial patient and examined it under microscope. He noticed some tiny living creatures. His discovery was not believed by other scientists but two years later another physician saw the same creatures in the same creatures in the blood of another malarial patient. Three years late after the second discovery the same creatures were observed for third time. The organism was given a name “malarial parasite” and then Plasmodium.

Biological Problem 1: What is the cause of malaria?


In the last part of the nineteenth century many different causes of malaria were being suggested. By that time there were for major observations about malaria.

  1. Malaria and marshy areas have some relationship.
  2. Quinine is an effective drug for treating malaria.
  3. Drinking the water of marshes does not cause malaria.
  4. Plasmodium is seen in the blood of malarial patients.


We know that a scientist uses whatever information and observation he has and makes one or more hypothesis. The hypothesis is made in this case was:

“Plasmodium is the cause of malaria”


Scientists does not know whether his hypothesis is true or not, but he accepts it may be true and makes deductions. One of the deductions from the above hypothesis was:

“If plasmodium is the cause of malaria, then all person ill with malaria should have plasmodium in their blood”.


The next step was to test the deduction through experiments which were designed as;

“Blood of 100 malarial patients was examined under microscope. For the purpose of having a control group, the blood of 100 persons was also examined under microscope.”


The results of the experiments showed that almost all malarial patients had plasmodium in their blood while 07 of 100 healthy persons also had plasmodium in their blood (now we know that plasmodium in the blood of healthy people was in incubation period the period between the entry of parasite in host and appearance of symptoms).


The results were quite convincing and proved that the hypothesis “Plasmodium is the cause of malaria” was true.

Biological problem 2:

How plasmodium gets into the blood of man?


Biologists were having following observations.”

  1. Malaria is associated with marshes.
  2. Drinking water of marshes does not cause malaria

From these observations it can be concluded that plasmodium was not in the marsh water. But it must be carried by something that comes to marsh water.

In 1883, a physician A.F.A king listed twenty observations. Some important observations of A.F.A king were:

People who slept outdoors were more likely to get malaria than those who slept indoors.

People who slept under fine nets were less likely to get malaria than those who did not use such nets’ and.Individuals who slept near a smoky fire usually did not get malaria.


On the basis of these observations king suggested a hypothesis.

“Mosquitoes transmit plasmodium and so are involved in the spread of malaria”.


Following deductions were made considering the hypothesis as true:

“If mosquitoes are involved in the spread of malaria the, plasmodium should be present in mosquitoes.”

“A mosquito can get plasmodium by biting a malarial patient”.


In order to test the above deductions Ronald Ross, a British army physician working in India in 1880’s, performed important experiments.

He allowed a female Anopheles mosquito to bite a malarial patient. He killed the mosquito some days later and found Plasmodium multiplying mosquito’s stomach.

The next logical experiment was to allow an infected mosquito (having Plasmodium) to bite a healthy person. If the hypothesis was true, the healthy person would have got malaria, but scientists avoid using human beings for experiments when the results can be so serious.

Ross used sparrows and redesigned his experiments. He allowed a female Culex mosquito to bite on the sparrows suffering from malaria. Some of the mosquitoes were killed and studied at various times. Ross found that Plasmodium multiplied in the wall of the mosquito’s stomach and then moved into the mosquito’s salivary glands. He kept some mosquitoes alive and allowed them to bite healthy sparrows. Female mosquitoes need the blood of mammals or birds for the maturation of their eggs. Ross found that the saliva of the infected mosquito contained Plasmodium and these entered the sparrow’s blood. When he examined the blood of these previously healthy sparrows, he found many Plasmodium in it.In the end, the hypothesis was tested by direct experimentation on human beings. In 1898 Italian biologists allowed an Anopheles mosquito to bite a malarial patient. The mosquito was kept for a few days and then it was allowed to bite a healthy man. This person later became ill with malaria. In this way, it was confirmed that mosquitoes transmit Plasmodium and spread malaria.

Transmission of Plasmodium:

When a female mosquito pierces the skin with her mouthparts, she injects a small amount of saliva into the wound before drawing blood. The saliva prevents the blood from clotting in her food canal.

  1. Write a comprehensive definition of theory, law or principle.

Ans. Theory:

        When a hypothesis is given a repeated exposure to experimentation and is not falsified, it increases biologists, confidence in the hypothesis. Such well-supported hypothesis may be used as the basis for formulating further hypothesis which are again proved by experimental results. The hypothesis that stand the test of time (often tested and never rejected), are called theories. A theory is supported by a great deal of evidence.

Law or principle:

Productive theory keeps on suggesting new hypothesis and so testing goes on. Many biologists take it as a challenge and exert greater efforts to disprove the theory. If a theory survives such doubtful approach and continues to be supported by experimental evidence, it becomes law or principle. A scientific law is a uniform or constant fact of nature. It is an irrefutable theory. The examples of biological laws are Hardy-Weinberg law and Mendel’s laws of inheritance.

  1. How the principles of ratio and proportion are used in biological method?

Ans. Data organization and data analysis:

Data organization and data analysis are important steps in the biological method.


Data can be defined as a single piece of information such as names, dates or values made from observations and experimentations.

Data organization:

In order to formulate and then to test the hypothesis scientists collect and organize data.


Variables are those factors being tested in an experiment and are usually compared to a control.


A control is known measure to which scientists can compare their results.

Prior to conducting an experiment it is very important for a scientist to describe the data collection methods. It ensures the quality of the experiment. Attention must be paid to ensure the data collection methods are kept balanced. Data is organized in different formats like graphics, tables, flow charts, maps and diagrams.

Data analysis:

Data analysis is necessary to prove or disprove a hypothesis by experimentation. The methods involved in testing/analyzing the data are also important since an experiment should be repeated by others to ensure the quality of results. Depending on the type of data and the biological problem, this might include application of statistical methods i.e. ratios and proportion.


When a relation between two numbers e.g. ‘a’ and ‘b’ is expressed in terms of quotient (a/b), such a relation is the ratio of one number to the other. A ratio may be expressed by putting a division ( ) or colon (:) mark between the two numbers. For example the ratio between 50 malarial patients are 150 normal persons is 1:3.


Proportion means to join the equal ratios by the sign of equality (=), For example; a: b=c: d is a proportion between the two ratios. This proportion may also be expressed as a: b: c: d.

In every proportion of two ratios are four terms i.e. the first and fourth terms are called extremes, the second and third are called means. So in the above proportion ‘a’ and ‘b’ are extremes while ‘b’ and ‘c’ are means. The basic rule used to solve problems through ratios and proportion is that the product of the extremes is equal to the product of means. When three values in a proportion are known, the fourth one (X) can be calculated by using this rule. For example a biologist can calculate how many birds would get malaria when he allows infected mosquitoes to bite 100 healthy sparrow. In the previous experiment he noted that when he allowed mosquitoes to bite 20 sparrows, 14 out of them got malaria. Now he uses the proportion rule.

Statistics are thus a means of summarizing data through the calculation of a:

1st ratio 14:20 (14 out of 20)                    Proportion 14:20:: X: 100  

2nd ratio X: 100 (how many out of 100)


It means 70 out of 100 sparrows would get malaria.

Mean value. This step is very important as it transforms raw data into information, which can be used to summarized and report results.

  1. Justify mathematics as an integral part of the scientific process?

Ans.                        Mathematics Scientific Processes

Applied Mathematics:

Biological method also involves the use of applied mathematics to solve biological problems. Major biological problems in which knowledge of mathematics is used include gene finding, protein structure, and protein-protein interactions, and the modeling of evolution.


Bioinformatics refers to the use of algorithms, computational and statistical techniques for the analysis of biological data. Computational biology refers to hypothesis driven investigation of a specific biological problem using computers.

Chapter # 3          BIODIVERSITY

Q.1. Tick the correct answer.                                
1. Classification means the grouping of organisms on the basis of?
(a) How they feed (b) The features they have in common (c) How they respire (d) How they can survive
2. The kingdom Protista includes?
(a) Unicellular and simple multicellular organisms with membrane bounded nucleus (b) True multicellular organisms with no distinct membrane bounded nucleus (c) True multicellular organisms with membrane bounded nucleus (d) Unicellular organisms with no distinct membrane bounded nucleus
3. Viruses are not classified in any kingdom because?
(a) They are too poorly understood (b) They are too small (c) Their genetic cannot be determined (d) They are not considered organisms
4. Viruses are assigned to the kingdom?
(a) Monera (b) Protista (c) Fungi (d) None of the above
5. A related group of genera comprises?
(a) An order (b) A family (c) A class (d) A phylum
6. In which kingdom would you classify unicellular eukaryotes?
(a) Fungi and protists (b) Fungi and Monera (c) Only Protista (d) Only fungi
7. In binomial nomenclature, the first letter of the …….. Name is capitalized?
(a) Family (b) Class (c) Species (d) Genus
8. Which one of the following sequences shows the correct hierarchy of classification, going from the smaller to the bigger group?
(a) Kingdom, phylum, order, class, family, genus, species (b) Kingdom, phylum, class, order, family, genus, species (c) Genus, species, kingdom, phylum, order, class, family (d) Species, genus, family, class, order, phylum, kingdom
9. Which of the following may be the correct way of writing the scientific name of an organisms?
(a) Canis lupis (b) Saccharum (c) Grant’s gazelles (d) E.coli
10. A certain organisms is multicellular, adapted for photosynthesis, and has multicellular sex organs. To which kingdom does it belong?
(a) Animals (a) Fungi (a) Plantae (a) Protista
11. Species that are in the same ……….. are most closely related than species that are in the same…….
(a) Phylum—- class (a) Family—- order (a) Class—- order (a) Family—- genus
12. When the last member of a particular species dies, the species is said to be…..
(a) Established (a) Extinct (a) Threatened (a) Endangered
13. In which season Houbara Bustard migrates to Pakistan and settle here?
(a) Summer (a) Spring (a) Autumn (a) Winter




Q2. Answer these short questions.

  1. Define biodiversity?

Ans. Diversity means variety within a species and among species. Biodiversity is a measure of the variety of organisms present in different ecosystem.

  1. Define biodiversity hotspot?

Ans. A biodiversity is a region with a high level of established species.

  1. What is taxonomy and systematic?

Ans. The branch of biology which deals with the classification is called taxonomy and the branch which deals with classification and also traced the evolutionary history of organisms is known as systematics.

  1. Write down the hierarchy amongst a kingdom?

Ans. Phylum:

(Division: for plants and fungi): A phylum is a group of related classes.


A class is a group of related orders.


An order is a group of related families.


A family is a group of related species.


A genus is a group of related species.


        A species consist of similar organisms.

  1. Define species?

Ans. A species is a group of organisms which can interbreed freely among them and produce fertile offspring, but are reproductively isolated from all other such groups in nature. Each species possesses its own distinct structural, ecological and behavioral characteristics.

  1. What is mule?

Ans. A cross between a male donkey and female horse produces as infertile offspring, the mule.

  1. Who proposed the earliest known classification?

Ans. The earliest known system of classification of organisms comes from the Greek philosopher Aristotle, who classified all living organisms known as that time as either in the group ‘plants’ or in ‘animals’.

  1. What is the contribution of Andrea Caesalpino in classification of plants?

Ans. Andrea Caesalpino (1519-1603) was an Italian botanist who proposed the first methodical arrangement of plants. He divided plants into fifteen groups called “genera”.

  1. Write distinguished characteristics of kingdom fungi?

Ans. It includes eukaryotic multicellular reducers for example mushrooms. Fungi are heterotrophic organisms that are absorptive in their nutritional mode. Most fungi are decomposers. They live on organic material, secrete digestive enzymes and absorb small organic molecules formed by the digestion by enzymes.

  1. What are prions and viroids?

Ans. Prions are composed of protein only and act as infectious particles in plants. Viroids are composed of circular RNA only and act as infectious particles and cause diseases in certain plants.

  1. Define binomial nomenclature?

Ans. Binomial nomenclature is the method of giving scientific to living organisms. As the word “binomial” suggests, the scientific name of species consists of two names; the first is the genus name and the second one is the name of the species.

  1. What is an extinct species?

Ans. A species is called extinct when there is no doubt that the last individual of that species has died.

  1. What is a threatened species?

Ans. A species is called threatened when it is at risk of exhibition in near future.

  1. What are different types of threatened species?

Ans. The threatened species may be:

  1. Vulnerable likely to become endangered unless the circumstances improve.
  2. Endangered at risk of becoming extinct because few members are left.
  • Critically endangered at extremely high risk of becoming extinct.
  1. What is domino effect?

Ans. Domino effects occur when the removal of one species (an extinction event) or the addition of one species (an invasion event) affects the entire biological system. Domino effects are especially likely when two or more species are highly interdependent.

  1. Define deforestation?

Ans. Deforestation means cutting down of trees for the conversation of a forest to non-forest land. It is done for using the land for various purposes such as pasture, urban use, etc.

  1. Which animals live in northern areas?

Ans. The northern areas provide habitats to Musk deer, snow leopard, Astore markhor and Himalayan ibex, woolly flying squirrel and the brown dear.

Q3. Answer the following long questions.

  1. What do you meant by biodiversity? Also write about the distribution of biodiversity or hotspots?

Ans. Biodiversity:

        The term “Biodiversity” has been derived from ‘bio’ and ‘diversity’. Formerly it was called ‘natural diversity’. “Diversity” means variety within a species and among species.

Biodiversity is a measure of the variety of organisms present in different ecosystem.

Plants, and animals, (flora and fauna) diversity depends on climate, altitude, soils and the presence of other species.

Biodiversity is not distributed evenly on Earth. It is richer in the tropics while there are fewer species in the polar region.

  1. Relate the importance of biodiversity with natural ecosystem through examples?

Ans. Importance of biodiversity:

Biodiversity provides food for humans. A significant proportion of drugs are derived, directly or indirectly, from biological sources. A wide range of industrial materials e.g. building materials, fibres, dyes, resins, gums, adhesive, rubber and oil are derived directly from biological resources.

Biodiversity plays important role in making and maintaining ecosystems. It plays a part in regulating the chemistry of our atmosphere and water supply. Biodiversity is directly involved in recycling nutrients and providing fertile soils.

  1. Explain the aims and principles of classification, keeping in view its historical background?

Ans. Classification-Aims and Principles:

There is a large collection of very dissimilar forms of organisms, found on earth. Over 1.5 million types of animals and over 0.5 million types of plants are known to biologists and these are only a small percentage of the total types estimated to live on earth.

Organisms range in complexity from small and simple bacteria to large and complex human beings. Some of them live in sea, some on land, some walk, others fly, and still others are stationary. Each has its own way of life i.e. getting food, avoiding unfavorable environmental conditions, finding a place to live, and reproducing its kind.

When we realize that there are so many diverse kinds of organisms, it becomes clear that no one can learn about the way of life of each.

To study such a large collection, biologist classify the organisms into groups and subgroups for this task they require some system. Biological classification is a method by which biologists group and categorize species of organisms.

Aims of Classification:

The branch of biology which deals with the classification is called taxonomy and the branch which deals with classification and also traces the evolutionary history of organisms is known as systematics.

The main aims of both these branches are:

  1. To determine similarities and difference among organisms so that they can be studied easily.
  2. To find the evolutionary relationships among organisms.

Basis of Classification:

Classification is based on relationship amongst organisms and such relationship is got through similarity in form or structure. These similarities suggest that all organisms are related to one another at some point in their evolutionary histories. However, some organisms are more closely related than others. For example sparrows are more closely related to pigeons than to the insects. It means that the former two have common evolutionary histories.

Biologists have classified all the known organisms into groups and subgroups on the basis of similarities. These similarities are seen in structures, biochemistry, cytology and genetics. Modern genetics provides another type of information to taxonomists. The genetic difference between two studied organisms can be determined and can be used for getting idea about similarities and differences in their structures and functions.

  1. Write descriptive note on taxonomic hierarchy?

Ans. Taxonomic Hierarchy:

The groups into which organisms are classified are known as taxonomic categories or taxa (singular “taxon”) and these taxa form a ladder, called taxonomic hierarchy. All the organisms are divided into five kingdoms.

Then, on the basis of similarities, each kingdom is further divided into smaller groups in the following ways:

  1. Phylum:

(Division: for plants and fungi): A phylum is a group of related classes.

  1. Class:

A class is a group of related orders.

  • Order:

An order is a group of related families.

  1. Family:

A family is a group of related species.

  1. Genus:

A genus is a group of related species.

  1. Species:

A species consists of similar organisms.

Each category is called taxon. It is more general than the one blow it and has emerged properties. Members of lower taxon resemble one another more than do the members of a higher taxon.

Species the Basic Unit of Classification:

        Species is the basic unit of classification. “A species is a group of organisms which can interbreed freely among them and produce fertile offspring, but are reproductively isolated from all other such groups in nature. “Each species possesses its own distinct structural, ecological and behavioral characteristics.

In the definition of species we must emphasize “in nature” because two organisms related to two different but closely related species can crossbred under artificial conditions. In such unnatural crosses they produce infertile offspring. A cross between a male donkey and female horse produces as infertile offspring, the mule.

The criteria of interbreeding apply primarily to those that regularly interbreed among themselves. However, it cannot be used as a criterion for species recognition in the group of organisms where asexual reproduction predominates and they do not interbreed with one another.

  1. Describe in detail the history of classification?

Ans. History of Classification Systems:

The earliest known system of classification of organisms comes from the Greek philosopher Aristotle, who classified all living organisms known at that time as either in the group ‘plants’ or in ‘animals’.

In 700s Abu-Usman Umer Aljahiz described the characteristics of 350 species of animals in his book. He wrote a lot about the life of ants.

Who was a judge (Qazi) in Seville, translated and abridged Aristotle’s book “de Anima (On the Soul)” into Arabic. His original commentary is now lost, but is translation into Latin is available.

In the last part of the 16th century and the beginning of the 17th, careful study of animals commenced, which served as an anatomical basis of classification.

Since late in the 15th century, a number of science authors had become concerned with the method of classification.

Some of them are:

  1. An Italian botanist Andrea Caesalpino (1519-1603) proposed the first methodical arrangement of plants. He divided plants into fifteen groups called “genera”.
  2. An English naturalist John Ray (1627-1705) published important works on plants classification.
  • Augusts Quirinus Rivinus (1652-1723 German botanist) and Pitton de Tournefort (1656-1708 French botanist) introduced the practice of naming the plants according to their genera.

Rivinus introduced the category of order and Tournefort introduced even more sophisticated categories of class, section, genus, and species.

Modern classification:

Modern classification has its root in the work of a Swedish biologist Carlos A. Linnaeus, who grouped species according to similar physical characteristics.

Biologists prefer the system that can provide maximum information about the basic differences and similarities among different organisms. According to earlier classification system, organisms were classified into two kingdoms but now taxonomists agree on five-kingdom classification system.

  1. Write down the distinguishing characteristics of two and three kingdoms of classification?

Ans. Two kingdom classification system:

It is the oldest system and classifies all organisms into two kingdoms:

  1. Kingdom Plantae
  2. Kingdom Animalia
  3. Kingdom Plantae:

According to two kingdom system, all organisms that can prepare food from simple inorganic materials and thus can store energy, are autotrophs and are included in kingdom plantae. According to this system, bacteria, fungi and algae were included in kingdom plantae.

  1. Kingdom Animalia:

According to two kingdom system of classification, the organisms that control synthesize their food and depend on autotrophs or others are heterotrophs and are included in kingdom Animalia.

Drawbacks of two kingdom system:

Some taxonomists found this system unknowable because:

Many unicellular organisms like Euglena have both plant-like (presence of chlorophyll) and animal-like (heterotrophic mode of nutrition in darkness and lack of cell wall) characters. So there should be separate kingdom for such organisms.

This system also ignores the difference between organisms having kingdom for such organisms.

Three kingdom classification system:

In 1866, Emst Haeckel solved the first objection and proposed a third kingdom, Protista to accommodate euglena-like organisms. He also included bacteria in kingdom Protista. In this system, fungi were still included in the kingdom plantae.

This system did not clear the difference between prokaryotes and eukaryotes. Some biologists disagreed about the position of fungi in kingdom plantae. Fungi resemble plants in many ways but are not autotrophs. They are special form of heterotrophs that get their food by absorption. They do not have cellulose in their cell walls rather possesses chitin.

  1. Write down the distinguishing characteristics of five kingdom system of classification?

Ans. Five kingdom classification system:

In 1937, E-Chatton suggested the terms of, “Procariotique” to describe bacteria and “Eucariotique” to describe animal and plant cells.

In 1967, Robert Whittaker introduced the five-kingdom classification system.

The system based on:

  1. The levels of cellular organization i.e. prokaryotic, unicellular eukaryotic and multicellular eukaryotic.
  2. The principal modes of nutrition i.e. photosynthesis, absorption, and ingestion.

On the basis, organisms are classified into five kingdoms:

  1. Monera
  2. Protista
  • Fungi
  1. Plantae
  2. Animalia

In 1988 Lynn Margulis and Karlene Schwartz modified the five-kingdom classification of Whittaker by considering cellular organization, mode of nutrition, cytology, genetics and organelles of symbiotic origin (mitochondria and chloroplast). They classified the organisms into the same five kingdom as proposed by Whittaker.

The five kingdoms:

The general characteristics of the five kingdom are as follows:

  1. Kingdom Monera:
  2. It includes prokaryotic organisms i.e. they are made of prokaryotic cells.
  3. Monerans are unicellular, although some types form chain, clusters, and eukaryotic cells.
  • Most are heterotrophic but some perform photosynthesis because they have chlorophyll their cytoplasm.


Within this kingdom there are two vastly different kinds of organisms i.e. archaebacterial and eubacteria. Many biologists believe that these two groups should be considered separate kingdoms.

  1. Kingdom Protista:

Kingdom Protista includes eukaryotic unicellular and simple multicellular organisms. There are three main types of protists.

  1. Algae are:

Unicellular, colonial or sometime simple multicellular. They resemble plant cells with cell walls and chlorophyll in chloroplasts. Simple multicellular means they do not have multicellular sex organs and do not from embryos during their life cycles.

  1. Protozoans:

Resemble animals whose cells back lack chlorophyll and cell walls.

Some protists are like the fungi.

  1. Kingdom fungi:
  2. It includes eukaryotic multicellular reducers for example mushrooms.
  3. Fungi are heterotrophic organisms that are absorptive in their nutritional mode.
  • Most fungi are decomposers. They live no organic material, secrete digestive enzymes and absorb small organic molecules formed by the digestion by enzymes.
  1. Kingdom plantae:
  2. It includes eukaryotic multicellular autotrophs.
  3. Plants photosynthesize their own food.
  • They have multicellular.
  1. They have multicellular sex organs and form embryos during their life cycles.


Mosses, ferns and flowering plants are included in this kingdom.

  1. Kingdom Animalia:
  2. It includes eukaryotic multicellular consumers.
  3. Animals live mostly by ingesting food and digesting it within specialized cavities.
  • They lack cell wall and show movements.
  1. How can you divide the five kingdom into two groups on the basis of types of cells?

Ans. Biologists believe that kingdom Protista evolved from Monera and then it gave rise to the other 3 eukaryotic kingdoms i.e. fungi, plantae and Animalia.

  1. Justify why virus are excluded from the five-kingdom classification system. Also write about prions and viroids?

Ans. Status of Viruses:

Viruses are acellular i.e. they do not possess cellular organization yet show some characters of livings. Viruses are infection entities which contain either RNA or DNA, normally encased in protein coat, and reproduce only in living cells, where they cause a number of diseases.

They are not considered as organisms and thus are not included in the live-kingdom classification system. Prions and viroids are also acellular particles and are not included in the five-kingdom classification system.


        Are composed of protein only and act as infections particles in plants.


Are composed of circular RNA only and act as infections particles and cause diseases in certain plants.

  1. Describe the aims and principles of binomial nomenclature?

Ans. Binomial Nomenclature:

Binomial nomenclature is the method of giving scientific to living organisms. As the word “binomial” suggests, the scientific name of species consists of two names; the first is the genus name and the second one is the name of the species.

Swedish biologist Carlos Linnaeus (1707-1778) first introduced and adopted the system of binomial nomenclature. His system spread rapidly and became popular. Many of his names are in use today.

Rules in Binomial Nomenclature:

There are certain rules which are universally adopted while suggesting and documenting the scientific names;

  1. Scientific names are usually printed in italics, such as Homo sapiens. When handwritten they are underlined.
  2. The first term (generic name) always begins with capital letter, while the species name is never capitalized (even when derived from a proper name).
  • The specific name is generally written in full when it is first used. But when several species from the same genus are being listed, it may then be abbreviated by just using an initial for the genus; for example Canis lupus becomes C. lupus.
  1. Sometime organisms are named in honor of the research workers who described and classified them for example the Orchid tree (Mountain-ebony) was named as Bauhinia variegata after the Swiss botanists Bauhin. Bauhinia variegata is an ornamental tree found in southeastern Asia.

Significance of Binomial Nomenclature:

Common names caused may problems.

Different names of same organism:

Various regions have different names for the same organism e.g. the common name of onion in Urdu is ‘Piyaz’ but in different regions of Pakistan it is also known as ‘ganda’ or ‘bassal’ or ‘vassal’. In other countries it has other sets of names.

Similarly ‘amaltas’ ‘argvad’ ‘gurmala’, ‘golden shower’ and ‘purging cassia’ are common names of the same plant.

Same names of different organisms:

In some cases several different organisms are called by the same common name, e.g. ‘Blue bell’ is used for dozens of plants with bell shaped flowers. Similarly ‘black bird’ is sued for crow as well as for raven.

Nonsense names:

Common names have no scientific basis. For example, to a biologist a fish is a vertebrate animal with fins and gills. But several common names of ‘silver fish’, ‘cry fish’, ‘jelly fish’, and ‘star fish’, do not fit the biologist’s definition of a fish.

The value of this system is due to widespread use and the stability of its names. In binomial nomenclature, every species can be unambiguously identified with just two words. The same name can be used all over the world, in all languages, avoiding difficulties of translation.


Common Name                                       Scientific Name

Onion                                                    Allium cepa

Common sea star                                    Asterias Rubens

House crow                                            Corvus splenders

  1. What do you meant by extinct species? Write examples of some extinct species in Pakistan?

Ans. Loss of Biodiversity:

During the last century, loss of biodiversity has been increasingly observed. Most species that have ever lived have gone extinct.

In the modern era, due to human actions, species and ecosystem are the threatened with destruction to an extent rarely seen in earth history.

Extinct Species:

A species that no longer lives in an ecosystem is said to be extinct in that ecosystem. When species of an ecosystem become extinct, the stability of ecosystem is harmed. Biologists warn that the global ecosystem would collapse if it is further reduced in complexity.

A species is called extinct when there is no doubt that the last individual of that species has died.

Extinct Animals in Pakistan:

Many species have been extinct in Pakistan within last few decades. The list of extinct animals in Pakistan includes lions, tigers, Asiatic cheetah, Indian one-horned rhinoceros, swamp deer, Indian wild ass, blackbuck and hangul, etc.

  1. Explain the impact of human beings on biodiversity?

Ans. Impact of Human Beings of Biodiversity:

The earliest that are clearly Homo sapiens, our species, are 500,000 years old. By 10,000 years ago there were about 5 million people on earth. More than 260,000 people are added to the world population each day, or more than 180 each minute!

With the advancement in agriculture and industry, the human population began to grow rapidly. Today around 600 million people live on earth.

To improve the living conditions for 600 million human, we are imposing serious threats to the survival of much biodiversity.

Some of the impacts of human beings on biodiversity are being discussed.

  1. Deforestation:

Deforestation means cutting down of trees for the conversion of a forest to non-forest land. The destruction of significant areas of forest has resulted in a degraded environment with reduced biodiversity.

Causes and effects of deforestation:

Sometime there is slow forest degradation and sometime sudden and catastrophic clear-cutting for urban development. Deforestation can be the result of deliberate removal of forests for wood, agriculture or urban development.

Deforestation affects the amount of water in soil and moisture in atmosphere. When there are no trees to keep soil in place, there are more chances of soil erosion. Heavy rainfall washes soil into rivers. Essential nutrients are washed out of soil. Rivers become choked up with mud and silt, which can cause floods. The silted water gets stored in dams and it reduces their water storage capacity. Deforestation also contributes to decreased transpiration, which lessens cloud formation. This ultimately reduces the sources of rains.

  1. Over-hunting:

Over-hunting has been a significance cause of the extinction of hundreds of species and the endangerment of many more, such as whales, ibex, markhor (the national animal of Pakistan) etc. commercial hunting, both legal and illegal, is the principal threat.

  1. What is the importance of forests?

Ans. Importance of Forests:

  1. Forests support considerable biodiversity, providing valuable habitat for wildlife.
  2. Forest look after medicinal conservation.
  • The utilization of forest products, including timber and fuel wood, have played a key role in human societies, comparable to the roles of water and land.
  1. Today, developed countries continue to utilize timber for building houses, and wood pulp for making paper.
  2. The forest products industry is a large part of the economy in both developed and developing countries.
  3. Short-term economic forests support considerable biodiversity, providing valuable habitat for wildlife.
  • Forests are also important stores of organic carbon, and forests can extract carbon dioxide pollutants from the air, thus contributing to biosphere stability.
  • Forests are also valued for aesthetic beauty and as a cultural resource and tourist attraction.
  1. In developing countries almost 3 billion people rely on wood for heating and cooking.
  2. Identify causes of deforestation and its effects on biodiversity?

Ans. Deforestation:

Deforestation means cutting down of trees for the conservation of a forest to non-forest land. It is done for using the land for various purposes such as pasture, urban use etc. the destruction of significance areas of forest has resulted in a degraded environment with reduced biodiversity.

Causes of deforestation:

  1. Sometimes there is slow forest degradation and sometime sudden and catastrophic clear-cutting for urban development.
  2. Deforestation can be the result of the deliberate removal of forests for agriculture or urban development.
  • Deforestation can be a consequence of grazing animals.
  1. The race to produced cash through fruits, species, sugar, tobacco, soap, rubber, paper and cloth has simulated many to get them by using soil and by destroying the forests.

Effects of deforestation:

  1. Deforestation affects the amount of water in the soil and the moisture in the atmosphere.
  2. When there are no trees to keep the soil in place, the soil becomes exposed for erosion.
  • There is less protection from wind and rain and heavy rainfall washes the soil into rivers.
  1. Essential nutrients are washed out of the soil all-together.
  2. Rivers becomes chocked up with mud and silt, which can cause floods.
  3. The silted water stored in dams and it reduces their water storage capacity and thus their lives.
  • Deforestation also contributes to decreased transpiration, which lessens cloud formation and less humidity. The ultimately reduces the sources of rains.
  1. Describe some of the programs running in Pakistan for the conservation of biodiversity?

Ans. Conservation of biodiversity:

The conservation of biodiversity has become a global concern. Biologists consider biodiversity essential and agree on the significance of current of species.

Though rich in biodiversity, Pakistan today faces severe threats for its biological resources. The greatest concern is the continuing loss of species the loss of natural habitats.

The international Union for the conservation of nature and natural resources (IUCN) and the world wildlife fund-Pakistan (WWF-P) work in close co-ordination with Pakistani’s Ministry of Environment and other government and non-government institutions. The IUCN has prepared the first national red list (list of endangered or threatened species).

According to this list following are the figures of the living and threatened species in Pakistan.

Table: Data about the living and threatened animal species in Pakistan.

Source Biodiversity Action Plan (IUCN)

Total Reported Threatened
Mammals 174 20
Birds 668 25
Reptiles 177 6
Amphibians 22 1
Fish (freshwater) 198 1
Fish (marine) 788 5


Following are a few examples of environmental of environmental work that has been carried out in Pakistan in order to converse species and the associated habitats.

  1. National Conservation Strategy:

In 1980’s the IUCN and the government of Pakistan formulated the National conservation strategy for Pakistan for the conservation of Pakistan’s biodiversity.

  1. UN Convention on Combating Desertification:

This is an international strategy against damage and poverty in dry lands. Pakistan signed this in 1997.

  1. Himalayan Jungle Project (HJP):

It started in 1991 Palas Valley, in NWFP. It aimed at protecting one of the richest areas of biodiversity in Pakistan.

  1. Conservation of biodiversity of the Suleiman Range, Baluchistan:

Suleiman Range Chilaghoza forest is the largest Chilghoza forest in the world. In 1992 the WWF-P started its conservation program.

  1. Northern Areas Conversation Project:

The northern areas of Pakistan serve as a habitat for a number of wildlife species. The survival of these species is under threat. The NACP is a project of WWF-P which is successful in implementing a ban on the hunting of these species.

  1. Conservation of migratory birds in Chitral, NWFP:

Chitral lies on the migratory route of several important bird species. These birds face enormous hunting pressure. WWF-Pakistan initiated efforts to reduce the hunting pressure in 1992. The efforts proved successful.

  1. Conservation of Chiltan Markhor:

Hazarganji National Park is located close to Quetta and is the only remaining habitat of Chiltan Markhor in the country. WWF-Pakistan developed the management plan of the park.

  1. Bear baiting in Pakistan:

Bear-baiting is an old game in the subcontinent that came with the Britishers. WWF-Pakistan has been successful in imposing a ban on this illegal practice. The government of Pakistan played an active role in putting an end to this cruel sport.

  1. Write a descriptive note on the endangered species in Pakistan?

Ans. Endangered Species in Pakistan:

Due to many human activities, the biodiversity in Pakistan is facing a great loss. In bear-baiting, the herders capture the bear cubs and sell them to the trainers who ultimately train them and sell to the gypsies. Here are a few examples of endangered species in Pakistan.

Indus Dolphin:

The Indus dolphin is a freshwater river mammal. According to WWF-P, only 600 animals of this species are left today in the Indus River in Pakistan. The population of this species declined because of various factors, including water pollution, poaching, and destruction of habitat.

Macro Polo Sheep:

Macro Polo sheep are scattered in the Karakoram Mountain and Hindu Kush. In Pakistan, they are mostly found in the Khunjerab National Park and adjoining areas. Their numbers have been rapidly decreasing in the last two decades. WWF-P has started projects for its conservation and identification of additional sites where Macro Polo sheep color.

Houbara bustard:

Houbara bustards are migratory birds that fly to Pakistan in winter season. The decline in its population is not only as a result of hunting but also due to the destruction of its natural habitats.

Chapter # 4          CELLS & TISSUES

Q.1. Tick the correct answer.                                
1. Which of these clues would tell you whether a cell is prokaryotic or eukaryotic?
(a) The presence or absence of a cell wall (b) Whether or not the cell is partitioned by internal membranes (c) The presence or absence of ribosomes (d) Whether or not the cell contains DNA
2. There are _____ micrometer (m) in one millimeter (mm)?
(a) 10 (b) 100 (c) 1000 (d) 1/1000
3. The plasma membrane does all these accept ______?
(a) Contains the hereditary material (b) Acts as a boundary or border for the cytoplasm (c) Regulates passage of material in and out of the cell (d) Functions in the recognition of self
4. Which of these materials is not a component of the plasma membrane?
(a) Phospholipids (b) Glycoproteins (c) Proteins (d) DNA
5. Cells walls are found in these organisms, except for _____ which all lack cell walls?
(a) Plants (b) Animals (c) Bacteria (d) Fungi
6. The _______ is a major component of plant cell walls?
(a) Chitin (b) Peptidoglycan (c) Cellulose (d) Cholesterol
7. Plants cells have _____ and _____ which are not present in animal cells?
(a) Mitochondria, chloroplasts (b) Cell membranes, cell walls (c) Chloroplasts, nucleus (d) Chloroplasts, cell wall
8. The _____ is the membrane enclosed structure in eukaryotic cells that contains the DNA of the cell?
(a) Mitochondrion (b) Chloroplast (c) Nucleolus (d) Nucleus
9. Ribosomes are constructed in the _____
(a) Endoplasmic reticulum (b) Nucleoid (c) Nucleolus (d) Nuclear pore
10. Rough endoplasmic reticulum is the area in a cell where_____ are synthesized?
(a) Polysaccharides (a) Proteins (a) Lipids (a) DNA
11. Smooth endoplasmic reticulum is the area in a cell where_____ are synthesized?
(a) Polysaccharides (a) Proteins (a) Lipids (a) DNA
12. The mitochondria functions in ______?
(a) Lipid storage (a) Protein synthesis (a) Photosynthesis (a) Cellular respiration
13. The thin extensions of the inner mitochondria membrane are known as_____?
(a) Cristae (a) Matrix (a) Thylakoids (a) Stroma




Q2. Answer the following short questions?

  1. State the cell theory?

Ans. Cell theory states that:

  1. All organisms are composed of one or more cells.
  2. Cells are the smallest living things, the basic unit of organization of all organisms.
  • Cells basis only by divisions in previously existing cells.
  1. What are the functions of leucoplasts and Chromoplasts?

Ans. Leucoplasts store reserved food material in the form of starch grain while components provide colors, other than green, to the plant.

  1. Differentiate between diffusion and facilitated diffusion?

Ans. Differentiate between diffusion and solute molecules from their higher concentration towards their lower concentration without any carries proteins while during facilitated diffusion, a classier protein is used to facilitate the movement of solute molecules from their higher concentration towards lower concentration.

  1. What is meant by hypertonic and hypotonic solutions?

Ans. A hypertonic solution is a solution in which solute concentration is relatively higher than the other solution. It has comparatively low water potential. A hypotonic solution is a solution in which solution and it was relatively high water potential.

Q3. Answer the following long questions.

  1. Write a note on microscope?

Ans. Microscope:

The use of microscope to observe very minute living organisms is known as microscopy.

First Microscope:

The first compound microscope was invented by Zacharias Janssen, in Holland in 1559. It was simply a tube with lenses at each end and its magnification from 3x to 9x.

Terms in Microscopy:

Two important terms are used in microscopy.

  1. Magnification
  2. Resolving power or Resolution
  3. Magnification:

Magnification is the increase in the apparent size of an object and it is an important factor in microscopy.

  1. Resolving power or resolution:

Resolution is the measure of the clarity object and it is an important factor in microscopy.

The human naked eye can differentiate between two points, which are at least 0.01mm apart. This is known as the resolution of human eye. If we place two objects 0.5mm apart, human eye would not be able to differentiate them as two separate objects.

The resolution can be increased with the help of lenses.

Two types of microscope i.e. light microscope (LM) and electron microscope (EM) are used in microscopy.

  1. Write the characteristic features of light microscope?

Ans. Light Microscope:

Source of illumination:

A specimen can be observed by passing visible light through it under a light microscope.


Light microscope uses two glass lenses. One lens produces an enlarged image of the specimen and the second lens magnifies the image and projects it into the viewer’s eye or onto photographic film. A photograph taken through a microscope is called micrograph. When we see a microscope on the page of a book, we observe some words like “LM 109x” printed along the edge of the micrograph means that this photomicrograph was taken through a light microscope and that the image has been magnified 109 times.


Magnification of a light microscope is 1500x as it can magnify objects only about 1500 times.


Resolving power of a light microscope is 0.2 micrometer ( ) and 1 =1/1000 mm. So, the light microscope cannot distinguish objects smaller than 0.2m. It is about the size of the smallest bacterium.

The image of bacterium can be magnified many times, but the light microscope cannot show the details of its internal structure.

To study the life processes e.g. movement of Amoeba a light microscope is better.

  1. Write the characteristics features of an electron microscope?

Ans. Electron Microscope:

Is the most advanced form of microscope?

Source of illumination:

In electron microscope, the object and the lens the object and the lens is place in a vacuum chamber and a beam of electrons is passed through the object. Electrons pass through or are reflected from the object and make image. Electromagnetic lenses enlarge and focus the image onto a screen or photographic film.

The electron microscope has much higher resolving power then light microscope. The most modern electron microscope can distinguish object as small as 0.2 nanometer (nm) and 1nm=1/1000000 mm. It is a thousand-fold improvement over the light microscope.

Under special conditions electron microscope can detect individual atoms. Cells, organelles and even molecules like DNA and protein are much larger than single atoms.

Electron microscope has revolutionized the study of cells and organelles. One problem with electron microscope is that it can’t be used to study life processes, because the specimen must be held in a vacuum chamber, i.e. all the air must be removed.

Types of Electron Microscopes:

Biologists use two types of electron microscopes.

  1. Transmission electron Microscope (TEM)
  2. Scanning electron Microscope (SEM)

Transmission electron Microscope:

Electron microscope is used to study the details of the internal cell structure. The TEM can magnify object about 250,000 times. In this microscopy specimen is cut into extremely thin sections. When electron beam is directed through the chamber, the electrons hit the specimen and are transmitted.

The lenses focus the transmitted electron beam onto a screen or photographic film for viewing.

Scanning Electron Microscope (SEM):

Is used to study the detailed architecture of cell surfaces. It uses an electron beam to scan the surface that has been coated with metal. When beam hits the metal. It is not absorbed or transmitted. Electrons are reflected from the metal and are collected and used to produce image.

The SEM does not have great magnifying power. It is about 10,000 to 100,000 times.

  1. Write down few differences between light microscope and electron microscope?

Ans. Difference between light Microscope and Electron Microscope:

Sr.# Characteristics Electron microscope Light microscope
1 Radiation source Electron Light
2 Wave length 0.005nm 400-700nm
3 Maximum resolution in practice 0.5nm 200nm
4 Maximum useful magnification X 250,000 on screen as image or photograph X 1500 with eye
5 Lenses Electromagnets (condenser and objective) Lens


  1. Write down the history of formulation of cell theory?

Ans. History of the formulation of cell theory:

Ancient Greeks were the first to make comprehensive attempts to organize the data of the natural world.

Work of Aristotle:

Aristotle presented organized observations to support the idea that all animals and plants are somehow related.

Later this idea gave rise to questions like “is there a fundamental unit of structure shared by all organisms?” But before microscope were first used in 17th century, no one knew with certainty that living organisms do share a fundamental unit i.e. cell.

Work of Robert Hooke:

Cells were first described by a British scientist, Robert Hooke is 1665. He used his self-made light microscope to examine a thin slice of cork. Hooke observed a “honeycomb” of tiny empty compartments. He called the compartments in the cork as “cellular”. His term has come to us as cells.

His remarkable engineering abilities enabled him to invent and improve many mechanical devices, including timepieces, the quadrant, and the Gregorian telescope. His observation about the section of cork is also illustrated here.

Work of Antonie van Leeuwenhoek:

The first living cells Leeuwenhoek. He observed tiny organisms (from pond water) under his microscope and called them as “animalcules”.

Work of Jean Baptist de-Lamarck:

In 1809, Jean Baptist de-Lamarck proposed that ‘nobody can have life if its constituent parts are not cellular tissues or are not formed by cellular tissues”.

Work of Robert Brown:

In 1831, a British botanist Robert Brown discovered nucleus in the cell.

Work of Matthias Schieiden:

In 1838, a German botanist Matthias Schieiden studied plant tissues and made the first statement of the cell theory. He stated that “all plants are aggregates of individual cells which are fully independent and separate beings”.

Work of Theodor Schwann:

In 1839, a German zoologist Theodor Schwann reported that all animal tissues are also composed of individual cells.

Thus Schieiden and Schwann proposed cell theory in its initial form i.e. “all living things are composed of living cells.”

Work of Rudolf Virchow:

In 1855, Rudolf Virchow, a German physician, proposed an important extension of cell theory. He proposed that all living cells arise from pre-existing cells (“Omnis cellula a cellula”).

Work of Louis Pasteur:

In 1962, Louis Pasteur provided the experimental proof of this idea.

The cell theory is regarded as one of the most fundamental generalization in biology. It has wide ranging effects in all field of research. After the initial presentation of the cell theory by Schieiden and Schwann, many details of cells were studied and cell theory was extended.

  1. State the salient features of cell theory?

Ans. The Cell Theory:

The cell theory includes the following principles:

  1. All organisms are composed of one or more cells, within which all life possesses occur.
  2. Cells are the smallest living things, the basic unit of organization of all organisms.
  • Cells arise only by divisions in previously exiting cells.
  1. What do you meant by sub-cellular or acellular particles?

Ans. Sub-cellular and Acellular Particles:

According to the first principle of the cell theory all organisms are composed of one or more cells. Discovery of virus, prions and viroids claim that the statement is not so universal. They are not composed of cells, rather they are sub-cellular or acellular particles, which do not run any metabolism inside them.

As they show some characteristics of living organisms i.e. they can increase in number and can transmit their characteristics to the next generations.

  1. Describe the structure of cell wall?

Ans. Cell Wall:

Following are few characteristics of a plant cell.

  1. The cell wall is a non-living structure.
  2. Cell wall is very strong component of the cell.
  • Cell wall is located outside the plasma membrane.
  1. It provides shape, strength, protection and support to the inner living matter (protoplasm) of the cell.
  2. Plant cells have a variety of chemicals in their cell walls.

Chemical Composition of Cell Wall

Primary Cell Wall:

The outer layer of the plant cell wall is known as primary wall and cellulose is the most common chemical in it.

Secondary Cell Wall:

Some plant cells, for example xylem cells, also have secondary walls on the inner side of the primary wall. It is much thicker and lignin and other chemicals are embedded in it.

Middle Lamella:

A middle lamella is present in between two adjacent cells as cementing material. It contains waxes, lignin, silica etc.


In the walls of neighboring cells, there are present cytoplasmic connections, called Plasmodesmata. Through these connections, cells transfer chemicals among each other. Fungi and many protists have cell walls although they do not contain cellulose. Their cell walls are made of a variety of chemicals. For example chitin is present in the cell wall of fungi. Prokaryotes have a cell composed of peptidoglycan that is a single large polymer of amino acids and sugar.

  1. Explain the functions of cell membrane?

Ans. Cell Membrane:

All prokaryotic and eukaryotic cells have a thin and elastic cell membrane covering the cytoplasm.

Functions of Cell membrane:

  1. The cells membrane functions as a semi-permeable barrier, allowing a very few molecules across it while fencing the majority of chemicals inside the cell.
  2. The membrane maintains the internal composition of the cell to a constant or nearly constant level.
  • Cell membrane can also sense chemical messages and can identify materials and other cells, etc.
  1. In eukaryotic cell many organelles e.g. mitochondria, chloroplasts, Golgi apparatus, and endoplasmic reticulum are also bounded by cell membranes.

Chemical Composition of Cell Membrane:

Chemically, cell membrane is mainly composed of proteins and lipids with small quantities of carbohydrates.

Fluid Mosaic Model:

Electron microscopic examinations of cell membranes have led to the development of the fluid-mosaic model of cell membrane.

According to Fluid Mosaic Model:

  1. Lipids are aligned in such a way that they make a bilayer. It gives fluidity and elasticity to the cell membrane.
  2. Proteins may be fully submerged in the lipid bilayer or some of them may “stick out” into the interior and outside of the cell. These proteins function as gateways that allow certain molecules to cross into and out of the cell.
  • Small amounts of carbohydrates are also found in cell membranes. These are joined with proteins (in the form of glycoproteins) or with lipids (in the form of glycolipids). Both these forms act as fingerprint of the cell.

Cholesterol, a lipid, is an important component of cell membrane embedded in the inner region of the lipid bilayer. Most bacterial cell membranes do not contain cholesterol.

  1. What is cytoplasm and what is its function?

Ans. Cytoplasm:


Cytoplasm is the material between the plasma membrane (cell membrane) and the nuclear envelope.


Cytoplasm is a semi-viscous and semi-transport substance. It contains water in which many organic (proteins, carbohydrates, lipids) and inorganic salts are completely or partially dissolved.


The cytoplasm of the cell provides space for the proper functioning of the organelles and also acts as the site for various metabolic reactions, for example Glycolysis (breakdown of glucose during cellular respiration.

  1. Write a short note on cytoskeleton?

Ans. Cytoskeleton:

The cytoskeleton is an important, complex, and dynamic cell component. It is invisible under light microscope. It maintains the cell’s shape, anchors organelles in place and moves parts of the cell in processes of growth and motility.

Two important types of filaments make up the cytoskeleton. These are:

  1. Microtubules
  2. Microfilaments
  3. Microtubules:

Microtubules are made of a protein called tubulin. These are used by cells to hold their shape. Microtubules are also the major component of cilia and flagella.

  1. Microfilaments:

Microfilaments are made up of a protein called actin. These microfilaments are approximately one-third of the diameter of a microtubule.

These microfilaments are often used by cells to change their shapes and to hold structures.

  1. What are cell organelles?

Ans. Cell Organelles:

Cell organelles are small structures within the cell cytoplasm that perform specialized functions. There are about a dozen types of organelles commonly found in eukaryotic cells, for example, mitochondria, vacuoles, centrioles, endoplasmic reticulum, Golgi bodies, etc.

  1. Write a descriptive note on structure and function of nucleus?

Ans. Nucleus:

Nucleus is present in all eukaryotic cells.


In animal cells it is present in the center while in mature plant cells, due to the formation of large central vacuole, it is pushed to side.

Nuclear envelope:

The nucleus is bounded by a double membrane known as nuclear envelope. The nuclear envelope contains many small pores that enable it to act as a differentially-permeable membrane.


Inside the nuclear envelope a granular matrix, the nucleoplasm, is present. The nucleoplasm contains one or two nucleoli and chromosomes.


Chromosomes are visible only during cell division while during cell division while during interphase (non-dividing phase) of the cell they are in the form of the thread-like structures known as chromatin. Chromosomes are composed of deoxyribonucleic acid (DNA) and proteins.

  1. Describe the structure and function of ribosomes?

Ans. Ribosomes:

Ribosomes are the only organelles found in all prokaryotic and eukaryotic cells.


Ribosomes are either floating freely in the cytoplasm or are bound to the endoplasmic reticulum (ER).


        Ribosomes are ting granular structures. Each ribosomes is made up of almost equal amounts of proteins and ribosomal RNA (rRNA). Ribosomes are not bound by membranes and so are also found in prokaryotes. Eukaryotes ribosomes are slightly larger than prokaryotic ones.

  1. Describe the structure and function of mitochondria?

Ans. Mitochondria:

Mitochondria are the double membrane-bounded structures found only in eukaryotes.

The outer membrane of mitochondria is smooth but the inner membrane forms many infoldings called cristae in the inner mitochondrial matrix. This serves to increase the surface area of the inner membrane on which membrane-bound reactions can take place.

Mitochondria have their own DNA and their own ribosomes, and those ribosomes are more similar to bacterial ribosomes than to eukaryotic ribosomes.


Mitochondria are the sites of aerobic respiration, and are the major energy production centers.

  1. Describe the structure and function of plastids?

Ans. Plastids:

Plastids are also membrane-bound organelles that only occur in plants and photosynthetic protists (algae).

Types of Plastids:

They are of three types:

  1. Chloroplasts
  2. Leucoplasts
  • Chromoplasts
  1. Chloroplast:

Chloroplast is also bound by a double membrane. The outer membrane is smooth while the inner one gives rise to membranous sacs called thylakoids (the stack of thylakoids is known as a garnurn floating in a fluid termed the stroma.

Chloroplasts are the sites of photosynthesis in eukaryotes. They contain chlorophyll, the green pigment necessary for photosynthesis, and associated accessory pigments. These pigments are present in thylakoids of the grana of chloroplasts.

  1. Chromoplasts:

They contain pigments associated with the bright colors and are associated with the bright colors and are present in the cells of flower petals and fruits. Their function is to give colors to these parts and thus help in pollination and dispersal of fruit.

  1. Leucoplasts:

Leucoplasts are colorless and store starch, proteins and lipids. They are present in the cells of those parts where food is stored.

  1. Describe the structure and function of endoplasmic reticulum and Golgi apparatus?

Ans. Endoplasmic Reticulum(ER):

Endoplasmic reticulum is a network of interconnected channels that extends from cell membrane to the nuclear envelopes.

  1. Rough endoplasmic reticulum:


Rough endoplasmic reticulum due to the numerous ribosomes that are attached to it. It connects to the nuclear envelope through which the messenger RNA (mRNA) travels to the ribosomes.


Due to the presence of ribosomes, RER serves a function in protein synthesis.

  • Smooth endoplasmic reticulum (SER):


Smooth endoplasmic reticulum (SER) lacks ribosomes thus gives smooth appearance.


It is involved in lipid metabolism and in the transport of materials from one part of the cell to the other. It also detoxifies the harmful chemicals that have entered the cell.

  1. Golgi Apparatus:


An Italian physician named Camillo Golgi discovered a set of flattened sacs (cisternae) that are stacked over each other. Golgi named this set of cisternae as Golgi apparatus. It is also called Golgi body or Golgi complex.


It is found in both plant and animal cells.


It modifies molecules coming from rough ER and packs them in to small membrane bound sacs called Golgi vesicles. These sacs can be transported to various locations in the cell or to its exterior, in the form of secretions.

  1. Describe the formation and function of lysosomes?

Ans. Lysosomes:


In the mid-twentieth century, they Belgian scientists Christian Rene de Duve discovered lysosomes. De Duve won the 1974 Nobel Prize for physiology and medicine.


        These are single-membrane bound organelles. Lysosomes contain strong digestive enzymes and work for the breakdown (digestion) of food and waste materials the cell.


A lysosomes fuses with the vacuole that contains the targeted material and its enzymes break down the material.

Here we can see an advantage of the compartmentalization of the eukaryotic cell. The cell could not support such destructive enzymes if they were not contained in a membrane bound lysosomes.

  1. Describe the structure and function of centrioles and vacuoles?

Ans. Centrioles:


Centrioles are present in animal cells and many unicellular organisms. Animal cells have two centrioles located near the exterior surface of the nucleus.


Centrioles have hollow and cylindrical organelles known as centrioles. They are made up of nine triplets of microtubules that are composed of an important protein, known as tubulin. The two centrioles are collectively called a centrosome.


Their function is to help in the formation of spindle fibers during cell division.

In cells that contain cilia and or flagella, centrioles are involved in the formation of cilia and flagella.



Vacuoles are fluid filled single-membrane bound organelles. Cells have many small vacuoles in their cytoplasm but in a plant cell small vacuoles absorb water and fuse to form a single large vacuole in the center. The cells in this state become turgid.


Many cells take in materials from outside in the form of food vacuole and then digest the material with the help of lysosomes. Some unicellular organisms use contractile vacuole for the elimination of wastes from their bodies.

  1. Write down the similarities and differences between prokaryotes and eukaryotes?

Ans. Similarities:

There are few similarities between prokaryotic and eukaryotic cells.

  1. They both have DNA as their genetic material.
  2. They are both membrane bound.
  • They both have ribosomes.
  1. They have similar basic metabolism.
  2. They are both amazingly diverse in form.

Difference a prokaryotic cell and eukaryotic cell

Prokaryotic Cell:

  1. Organisms:

The organisms made of prokaryotic cell are called prokaryotic e.g. bacteria and cyanobacteria.

  1. Nucleus:

Chromosomes are present in the cytoplasm and no membrane bounded nucleus in present.

  • DNA:

The DNA of a prokaryotic cell floats in cytoplasm near the center in a region called nucleoid.

The DNA of prokaryotes is not complex and extensive.

  1. Organelles:

No membrane bounded cell organelles are present.

  1. Ribosomes:

Ribosomes are of small size and freely scattered in cytoplasm.

  1. Cell wall:

Cell wall is composed of peptidoglycan or murein. Cellulose in absent.

  • Division of labor:

There is usually no division of labor in prokaryotic cells.

  • Size:

These cells are simple, comparatively smaller in size (average, diameter 0.5/10nm).

  1. Examples:


Eukaryotic Cell:

  1. Organisms:

The organisms made of eukaryotic cell are called eukaryotic e.g. animal, plants, fungi and protests.

  1. Nucleus:

Chromosomes are present in membrane-bounded nucleus.

  • DNA:

The DNA of eukaryotic cells in held within the nucleus.

The DNA of eukaryotes is much more complex and extensive.

  1. Organelles:

Membrane bounded organelles are present.

  1. Ribosomes:

Ribosomes are of large size and are present on endoplasmic while in fungi it is of chitin.

  1. Cell wall:

Cell wall of plant cell is composed of cellulose while in fungi it is of chitin.

  • Division of labor:

There is much higher level of intracellular division of labor in eukaryotic cells.

  • Size:

These cells are complex comparatively larger in size (average diameter 10-100nm).

  1. Examples:

Animal cell

  1. What are the major difference between an animal cell and a plant cell?

Ans.         Differences between a animal cell and plant cell.

Animal Cell:

  1. Cell wall:

A cell membrane is the outer most boundary of an animal cell. Cell wall is absent.

  1. Centrioles:

Centrioles are present in animal and lower plant cells.

  • Vacuoles:

An animal cell may contain numerous small sized vacuoles.

  1. Position of nucleus:

The position of nucleus is usually central.

  1. Plastids:

There are no plastids in animal cell and hence they cannot manufacture their own food material.

Plant Cell:

  1. Cell wall:

A cell wall is the outer most boundary of a plant cell.

  1. Centrioles:

Centrioles are absent in higher plant cells.

  • Vacuoles:

A plant cell has one or few large sized vacuole.

  1. Position of nucleus:

Due to a large vacuole nucleus is pressed aside towards the cell membrane.

  1. Plastids:

Plastids are present in plant cells and hence they can manufacture their own food material.

  1. State the relationship between cell function and cell structure?

Ans. Relationship between cell function and cell:


The bodies of animals and plants are made of different cell types. Each type performs specific function and all coordinated functions become the life processes of the organism.

Cells of one type may differ from those of other types in following respects.

Size and shape:

Nerve cells are long for the transmission of nerve impulse. Xylem cells are tube-like and have thick walls for conduction of water and support.

Red blood cells are round to accommodate globular haemoglobi.

Surface area to volume ratio:

Root hair cells have large surface area for the maximum absorption of water and salts.

Presence or absence of organelles:

Cells involved in making secretions have more complex ER and Golgi apparatus. Cells involved in photosynthesis have chloroplasts.

We can imagine the specialists of different cell types and the contribution of individual calls to the healthy functioning of the body.

For example in human body:

  1. Nerve cells conduct nerve impulse and thus contribute in coordination in body.
  2. Muscle cells undergo contraction and share their role in movements in body.
  • Red blood cells carry oxygen and white blood cells kill foreign agents and so contribute in the roles of blood in transportation and defense.
  1. Some skin cells act as physical barriers against foreign materials and some as receptors for temperature, touch, pain etc.
  2. The cells of bone deposit calcium in their extracellular spaces to make the bone tough and thus contribute to the supporting role of bones.

A cell works as an open system i.e. it takes in substances needed for its metabolic activities through its cell membrane. Then it performs the metabolic processes assigned to it. Products and by-products are formed by in metabolism. Cell either utilizes the products or transports them to other cells. The by-products are either stored are excreted out of the cell.

  1. Explain how surface area to volume ratio limits cell size?

Ans. Cell Size & Surface Area to Volume Ratio:

Cells very greatly in size. The smallest cells are bacteria called mycoplasmas, with diameter between 0.1m to 1.0m. The bulkiest cells are bird eggs, and the longest cells are some muscle cells and nerve cells. Most cells lie between these extremes.

Cell size and shape are related to cell function. Bird eggs are bulky because they contain a large amount of nutrient for the developing young. Long muscle cells are efficient in pulling different body parts together. Lengthy nerve cells can transmit nerve signals between distant parts of animal’s body.

Small cell size also has many benefits. For example human red blood cells are only 8m in diameter and therefore can move through our tiniest blood vessels.

Most cells are small in size. Large cells have less surface area in relation to their volume while small cells of the same shape have more surface area.

The figure below shows 1 large cell and 27 small cells, in both cases the total volume is the same.

Volume= 30m x 30m x 30m= 27,000 m3

In contrast to the total volume, the total surface areas are very different. Because the cubical shape has 6 sides, its surface area is 6 times the area of 1 side.

The surface areas of the cubes are as follows:

Surface area of 1 large cube= 6x (30mx30m) =5400m3

Surface area of 1 small cube= 6x (10mx10m) =600m2 and

Surface area of 27 small cubes = 27x 600m2 = 16,200m2

This relationship between cell size and surface area to volume ratio works to limit cell size. As the size of a cell increases, cell volume increases more rapidly that its surface area. The need of nutrients and rate of waste production are directly proportional to cell volume. The cell takes up nutrients and excretes wastes through its surface cells membrane. So a large volume cell demands large surface area. But a large cell has a much smaller surface area relative to its volume than smaller cells have.

Hence was concluded that the membranes of small cells can serve their small volumes more easily than the membrane of large cell.

  1. Explain the phenomenon involved in the passage of matter across cell membrane?

Ans. Passage of molecules into and out of calls:

Cell membrane are called differentially or semi-permeable membranes as they separate the inner cellular environment from the outer environment. While exchanging matter with cell’s environment, cell membranes maintain equilibrium inside the cells as well as outside. This control of the passage of molecules into and out of cells is made possible through following phenomena:

  1. Diffusion
  2. Facilitated diffusion
  • Osmosis
  1. Filtration
  2. Active transport
  3. Endocytosis
  • Exocytosis
  1. Diffusion:


Diffusion is the net movement of a substance from an area of higher concentration to the area of lower concentration i.e. along concentration gradient without the expense of energy hence the diffusion is type of passive transport.


Since the molecules of any substance (solid, liquid, or gas) are in motion when that substance is above 0 degree Kelvin or -273 degrees C, energy is available for movement of the molecules from a higher potential state to a lower potential state. In a substance the majority of the molecules move from higher to lower concentration, although there will be some that move from low to high. The overall (or net) movement is thus from high to low concentration. Eventually, if no energy is input into the system the molecules will reach a state of equilibrium where they will be distributed equally throughout the system.

Because a cell does not expend energy when molecules diffuse across its membrane.


Diffusion is one principle method of movement of substances within cells, as well as the method of essential small molecules to cross the cell membrane. Carbon dioxide and oxygen are among the few simple molecules that can cross the cell membrane by diffusion. Gas exchange in gills and lungs operates by this process.

  1. Facilitated diffusion:

Many molecules do not diffuse freely across cell membranes because of their size or charge. Such molecules are taken into or out of the cells with the help of transport-proteins present in cell membranes. When one of these transport proteins makes it possible for a substances to move it down its concentration gradient (from higher to lower concentration), the process is called facilitated diffusion. The rate of facilitated diffusion is higher than simple diffusion.

Facilitated diffusion is also a type of passive transport because there is no expenditure of energy in this process.

  1. Osmosis:

Osmosis is the movement of water across a selectively permeable membrane from a solution of lesser solute concentration to a solution of higher solute concentration.

The rules of osmosis can be best understood through the concept of tonicity of the solutions. The term tonicity refers to the relative concentration of solutes in the solutions being compared.

Hypertonic solutions are those in which more solute is present.

Hypertonic solutions are those with less solute.

Isotonic solutions have equal concentration of solutes.

In a hypertonic solution the solute molecules attract clusters of water molecules, so that fewer water molecules are free to diffuse across the membrane.

In a hypertonic solution with fewer solute molecules, there are more free water molecules and there is net movement of water from hypotonic solution to the hypertonic solution.

Water balance problems

Water balance problems in animals:

When an animal cell, such as the red blood cell, is placed in an isotonic solution, the cells volume remains constant because the rate at which water is entering the cell is equal to the rate at which it is moving out.

When a cell is placed in a hypotonic solution (which has lower salt concentration than the cell) water enters and the cells swells and may rupture like an over-filled balloon.

An animal cell placed in a hypotonic solution (which has higher salt concentration that the cell) will lose water and will shrink in size.

So in hypotonic environments (freshwater) animal cells must have ways to prevent excessive entry of water and in hypertonic environments (seawater) they must have ways to prevent excessive loss of water.

Water balance problems in plants:

Water balance problems are somewhat different for plant cells because of their rigid cell walls. Most plant cells live in hypotonic environment because there is low concentration of solutes in extracellular fluids that in their cells. As a result water tends to move first cytoplasm presses firmly against the interior of the cell wall, which expands a little. Due to strong cell wall, plant cell does not rupture but instead becomes rigid. The internal pressure of such a rigid cell is known as turgor pressure and this phenomenon is known as turgor.

In isotonic environment the planet cell is flaccid (loose/not firm), because the net uptake of water is not enough to make turgid. In a hypertonic environment a plant cell loses water, causing the cytoplasm to shrink within the cell wall. The shrinking of cytoplasm is called plasmolysis.

Stomata (openings) in leaf epidermis are surrounded by guard cells. During daytime guards cells are making glucose and so are hypertonic (have higher concentration of glucose) than their nearby epidermis cells. Water enters them from other cells and they swell. In this form they assume a rigid bowed shape, creating a pore between them. At night when there is low solute concentration in guard cells water leaves them and they become flaccid. In this form both guard cells rest against one another, closing the opening. We will learn more about the opening of stomata in chapter 9.

The knowledge about semi-permeable membranes is applied for various purposes. We know that semi-permeable membrane is capable of separating substances when a driving force is applied across it. Artificially synthesized semi-permeable membranes are used for separation of bacteria from viruses, because bacteria cannot cross a semi-permeable membrane. In advanced water-treatment technologies membrane-based filtration systems are used. Semi-permeable membranes efficiently separates slats from water under pressure.

  1. Filtration:

Filtration is a processes by which small molecules are forced to move across semi-permeable membrane with the aid of hydrostatic (water) pressure of blood pressure.

For example in the body of an animal, blood pressure forces water and dissolved molecules to move through the semi-permeable membranes of the capillary wall cells. In filtration the pressure cannot force large molecules, such as proteins, to pass through the membranes pores.

  1. Active transport:

Active transport is the movement of molecules from as area of lower concentration to the area of higher concentration. This movement against the concentration gradient requires energy in the form of ATP.

In this process, carrier proteins in the cell membranes use energy to move the molecules against the concentration gradient. For example the membranes of nerve cells have carrier proteins in the form of “sodium-potassium pump”. In a resting (not conducting nerve impulse) nerve cell, this pump spends energy (ATP) to maintain higher concentration of K+ and lower concentration of Na+ inside the cell. For this purpose, the pump actively moves Na+ to the outside of the cell where they are already in higher concentration. Similarly this pumps moves K+ from outside to inside the cell where they are in higher concentration.

  1. Endocytosis:

It is a special type of movement of material across cell membranes. In endocytosis bulky materials, rather than individual molecules, are moved across the cell membrane.

Endocytosis occur in following steps:

  1. A portion of cell membrane invaginates (depressed inward).
  2. The material from outside is taken inside the invagination.
  • The open ends of the invagination seal and form a small vesicle.
  1. The vesicle detaches from the cell membrane and moves into the cytoplasm. The two forms of endocytosis are phagocytosis (cellular eating) and pinocytosis (cellular drinking).

In phagocytosis cell takes in solid materials. In pinocytosis cell takes in liquid in the form of droplets.

  1. Exocytosis:

It is the process through which bulky material is exported. Exocytosis occurs in following steps:

  1. The bulky material is packed inside a membrane and a vesicle is formed.
  2. The vesicle moves to the cell membrane.
  • The vesicle fuses with the membrane and releases its contents into the extracellular environment.

This process adds new membrane which replaces the part of cell membrane lost during endocytosis.

  1. Describe the major animal tissues (epithelial, connective, muscular and nervous) in terms of their cell specificities, locations and functions?

Ans. Animal tissues:

There are four major categories of tissues in the bodies of animals:

  1. Epithelial tissue
  2. Connective tissue
  • Muscle tissue
  1. Nervous tissue
  2. Epithelial tissue:

Epithelial tissue covers the outside of the body and lines organs and cavities. The cells in this type of tissue are very closely packed together and joined with little space between them. Epithelial tissue helps to protect organisms form microorganisms, injury and fluid loss.

These tissues are commonly classified on the base of the shape of the cells as well as the number of cell layers. Some types include:

  1. Simple Squamous Epithelium:

A single layer of tightly packed, flattened cells. Found in lining of air sacs of the lungs, heart and blood vessels etc. Allow diffusion and filtration.

  1. Simple Cuboidal Epithelium:

Consists of single layer of tightly packed, cube-shaped cells. Found in kidney tubules, ducts and small glands. Makes secretions and absorbs materials.

  1. Simple Columnar Epithelium:

Consists of single layer of elongated cells. Found in the lining of digestive tract and gallbladder etc. Makes enzymes secretions.

  1. Ciliated Columnar Epithelium:

A tuft of cilia is present at the top of each columnar cell. Found in the lining of trachea and bronchi. Propels mucous by ciliary action.

  1. Stratified Squamous Epithelium:

Consists of many layers of flattened cells. Found in the inner lining of esophagus, mouth, and at the surface of the skin. Protects underlying tissues from abrasion.

  1. Connective tissues:

As the name implies, connective tissue serves a “connecting” function. It supports and birds other tissues. Unlike epithelial tissue, connective tissue typically has cells scattered throughout extracellular matrix. There are many types of this tissue.

  1. Loose connective tissue:

Most common type, matrix contains loosely arranged collagen (a protein) widely distributed under epithelial tissues.

  1. Fibrous connective tissue:

Matrix contains tightly packed collagen fibers. Found in tendons, which attach muscles and bones, and ligaments, which join two bones.

  1. Adipose tissue:

Swollen cells due to the presence of larger number of fat droplets. Found around kidneys, under skin, in abdomen etc. providers energy when fat is oxidized, insulates against heat loss, protects and support organs.

  1. Cartilage:

Matrix contains bundles of collagen fibers embedded in a rubbery substance.

Found around the ends of bones, in external ear, in noes, trachea, in discs between vertebrae (bones of vertebrae column), as skeleton in many fishes. Provides support while allowing flexibility.

  1. Bone:

Matrix contains collagen fibers embedded in calcium salts. Found in skeleton. Supports, projects, provide lever system for movements, stores calcium and forms blood cells.

  1. Blood:

Matrix is not solid but in the form of fluid (plasma), red and white blood cells are suspended in plasma.

Found in blood vessels.

Transports substances from one part of the body to the other and responsible for immunity.

  1. Muscle tissue:

Muscle tissue consists of bundles of long cells called muscle fibres. It is the most abundant tissue in a typical animal. The cells of this tissue have ability to contract.

Types of Muscle tissue:

There are three kinds of tissues in vertebrates:

  1. Skeletal muscles
  2. Smooth muscles
  • Cardiac muscles
  1. Skeletal muscles:

Composed of striated (striped) cells that are long and cylindrical and contain many nuclei.

Found attached to bones e.g. bicep muscle.

Responsible for voluntary movements and locomotion. The skeletal muscles are voluntary in action. i.e. their contraction is under the control of our will.

Exercise does not increase the number of our skeletal muscle cells, it simply enlarges those already present.

  1. Smooth muscles:

Composed of non-striated (smooth) cells that are spindle shaped and each contains a single nucleus.

Found in the walls of digestive tract, urinary bladder, blood vessels.

The smooth muscles are involuntary in action i.e. their contraction is not under the control of our will.

Moves substances (foodstuff, urine) along internal massage ways.

  1. Cardiac muscles:

Composed of striated cells that are branched and each contains a single nucleus.

Found in the walls of the heart.

Produce heartbeat that propels blood into the circulation.

The cardiac muscles are involuntary in action i.e. their contraction is not under the control of our will.

  1. Nervous tissue:

An animal’s survival depends on its ability to respond appropriated to stimuli from its environment. This ability requires the transmission of information from one part of the body to another. Nervous tissue forms a communication system and performs this task.

This tissue is mainly composed of nerve cells, or neurons, which are specialized to conduct messages in the form of nerve impulses. Nervous tissue is found in brain, spinal cord and nerves.

Nervous tissue:

Composed of elongated cells. Found in nerves, spinal cord and brain. Responsible for communication among body parts.

  1. Describe the major plant tissues i.e. simple tissues and compound tissues in terms of their cell specificities, locations and functions?

Ans. Plant tissues:

As animals, the cells of plants are grouped into tissues with characteristics functions such as photosynthesis, transport etc.

Kinds of plant tissues:

There are two major categories of tissues in plants.

  1. Simple tissues
  2. Compound (complex) tissues
  3. Simple tissues:

The tissues which are made of single type of cells are called simple tissues. They are two types:

  1. Meristematic tissues
  2. Permanent tissues
  3. Meristematic tissues:

These tissues are composed of cells, which have the ability to divide. The cells of meristematic tissues show following properties.

  1. They have thick cytoplasm, with large nucleus in the center and with small or no vacuoles.
  2. They are thin-walled.
  • They are all alike and there are no intercellular spaces among them.
  1. In plants cell division occurs solely in meristematic regions.

Two main types of meristematic tissues are recognized in plants.

  1. Apical meristems:

These are located at the apices or tips of roots and shoot. When they divide they cause increase in the length of plant. Such a growth is called primary growth.

  1. Lateral meristems:

These are located on the lateral sides of roots and shoot. By dividing they are responsible for horizontal expansion of the parts of plant. Such a growth is called secondary growth.

Lateral meristems are further of two types.

  1. Vascular cambium:

Vascular cambium is present between the xylem and phloem tissues. Its cells divide and form new xylem tissue toward the center and new phloem tissue towards the outside.

  1. Cork cambium:

Cork cambium is present in the outer lateral sides and its cells are responsible for making the characteristics corky layer.

Intercalary meristem occurs in the form of small patches of meristem present among the mature tissues. These are common in grasses and help in the regeneration of parts removed by herbivores etc.

  1. Permanent tissues:

Permanent tissues originate from the meristematic tissue. These tissues are composed of cells, which do not have the ability to divide. They are further classified into following types:

  1. Epidermal tissues:

Epidermal tissues are composed of a single layer of cells and they cover the plant body. They act as a barrier between the environment and the internal plant tissues. They are also responsible for the absorption of water and minerals primarily in the root region. On stem and leaves they secrete cutin (the coating of cutin is called cuticle) which prevents evaporation.

Roots hairs:

Absorb water and minerals.

Leaf hairs:

(1-2 cells) reflect light to protect against overheating and excessive water loss. They layer of leaf hairs acts to hold in a layer of humidity ‘trapped’. This layer also prevents air moving directly against the stomata which would encourage water loss. Leaf hairs reflect light and are important for plants in dry regions. Here excess light may lead to photo bleaching of pigments and excess absorption may overheat the tissues.


Are made by guard cells and are most abundant on underside of leaves. They regulate diffusion of  into the leaf for photosynthesis as well as regulate loss of water from the leaf.


Glands are the waste-bins for the excess salt absorbed from the soil. They form a crust of salt on leaves which results reflects light to prevent overheating.

  1. Ground tissues:

Ground tissues are simple tissues made up of parenchyma cells. Parenchyma cells are the most abundant cells in plants.

Overall they are spherical but flat at point of contact. They have thin primary cell walls and have huge vacuoles for storage of food. In leaves they are called mesophyll and are the sites of photosynthesis. In other parts they are the sites of respiration and protein synthesis.

  1. Support tissues:

These tissues provide strength and flexibility to the plants. They are further of two types.

  1. Collenchyma tissue:

They are found just beneath the epidermis in the cortex of young herbaceous stems and in the midribs of leaves and in petals of flowers. They are made of elongated cells with unevenly thickened primary cell walls. They are flexible and function to support the organs in which they are found.

  1. Sclerenchyma tissues:

They are composed of cells with rigid secondary cell walls. The cell walls are hardened with lignin, which is the main chemical component of wood. Mature sclerenchyma cells cannot elongate and most of them are dead. There are two types of cells in sclerenchyma tissues.

  1. Fibre cells are associated with xylem and phloem tissues.
  2. Scleride cells are found in seed coats.
  3. Compound (Complex) tissues:

A plant tissue composed of more than one type of cell is called a compound or complex tissue. Xylem and phloem tissue, found only in vascular plants, are examples of compound tissues.

  1. Xylem tissue:

Xylem tissue is responsible for the transport of water and dissolved from roots to the aerial parts. Due to the presence of lignin, the secondary walls of its cells are thick and rigid. That is why xylem tissue provides support to the plant body. Following types of cells are found in xylem tissue.

  1. Vessel elements or cells:

These are short and wide cells with thick secondary cell walls. The vessel cells are dead and hollow. They lack end walls and join together to form long tissues.

  1. Tracheids:

These are long, slender cells with overlapping ends. Water moves upward from tracheid to tracheid.

  1. Phloem tissue:

Phloem tissue is responsible for the conduction of dissolved organic matter (food) between different parts of the plant body. Following types of cell are found in phloem tissue.

  1. Sieve tube cells:

These are long cells. Their end walls have small pores and are called sieve plates. Many sieve cells join to from long pipelines called sieves tubes. During development they lose their nucleic and ribosomes etc and possess little protoplasm.

  1. Companion cells:

Each sieve tube cell is accompanied by a companion cell. The companion cells contain functional DNA and ribosomes and they make proteins for the sieve tube cells.


Cell specificities, location and functions of plant tissue.

Ch#5          CELL CYCLE

Q.1. Tick the correct answer.                                
1. In which stage of the cell cycle each chromosomes is duplicated and so it consists of two chromatids?
(a) G1 (b) S (c) M (d) G2
2. If you observe a cell like this one, what phase of mitosis is it?
(a) Anaphase (b) Telophase (c) Metaphase (d) Prophase
3. During which phase of mitosis spindles are formed?
(a) G2 (b) Interphase (c) Prophase (d) Metaphase
4. In which stage of the cell cycle, the cell is preparing to begin DNA replication?
(a) G1 (b) G2 (c) S (d) M
5. Which of the following features of cell division are very different for animal and plant cells?
(a) Prophase (b) Metaphase (c) Anaphase (d) Cytokinesis
6. Prior to cell division, each chromosome replicates or duplicates its genetic material. The products are connected by a centromere and are called?
(a) Sister chromosomes (b) Homologous chromosomes (c) Sex chromosomes (d) Sister chromatids
7. The process of mitosis ensures that?
(a) Each new cell is genetically different from its parent (b) Each new cell receive the proper number of chromosomes (c) Cell will divide at the appropriate time (d) DNA is replicated without errors
8. Cytokinesis in a plant cell is characterized by?
(a) The equal division of homologous chromosomes (b) A pinching off a cell membrane to divide to the cell (c) The formation of the cell plate in the cytoplasm (d) The movement of the chromosomes from the metaphase plate
9. Which of the following is unique to mitosis and not a part of meiosis?
(a) Homologous chromosomes pair forming bivalents (b) Homologous chromosomes cross over (c) Chromosomes pairs are broken during anaphase (d) Chromatids separate during anaphase
10. Which event distinguishes meiosis from mitosis?
(a) Condensation of chromosomes (a) Loss of the nuclear membrane (a) Formation of metaphase plate (a) Pairing of homologous chromosomes
11. In which stage of cell cycle most cells spend their lives?
(a) Prophase (a) Metaphase (a) Interphase (a) Telophase
12. Which of the following distinguishes meiosis from mitosis?
(a) In meiosis, the chromosome number is reduced (a) In meiosis, the daughter cells are genetically different from the parent cell (a) In meiosis, at least some of the daughter cells differ genetically from each other (a) All of the above
13. Between two mitotic divisions, the DNA of the cells is duplicated. When does DNA get duplicated during meiosis I and meiosis II?
(a) The DNA is duplicated between meiosis I and meiosis II (a) The DNA is duplicated during meiosis I and meiosis II (a) The DNA is duplicated during meiosis I (a) The DNA is duplicated during meiosis II



Q2. Answer the following short question.

  1. A nerve cell does not divide after its formation. In which phase of cell cycle it is?

Ans. The nerve cell is in G0 phase of interphase.

  1. How is cytokinesis different in plant cells as compared to animal cell?

Ans. During cytokinesis of animal cell, a cleavage furrow develops and deepens and eventually pinches the parent cell into two daughter cells white a membrane bounded cell plate or phragmoplates is formed in the middle of the plant cell and grows outwards. Eventually, the cell plate fusses with cell membrane, which results in two daughter cells.

  1. What type of cell division occurs when our wounds are healed?

Ans. Mitosis heals the wound.

  1. Plants do not make their gametes by meiosis. How is that?

Ans. The sporophyte generation of plants undergo incises to produce haploid spores, which grow into haploid gametophyte, in which haploid gametes are produced through mitosis, not meiosis.

Q3. Answer the following long questions.

  1. What is the cell cycle and what are its main phases?

Ans. Cell cycle:

The cell cycle is the series of events from the time a cell is produced until it completes mitosis and produces new cells.

Phases of cell cycle:

The cell cycle consists of two major phases.

  1. Interphase:

Interphase is the time when a cell’s metabolic activity is very high, as it performs its various functions. Typically, interphase lasts for at least 90% of the total time required for the cell cycle.

  1. Mitotic phase (M phase):

The mitotic phase is a relatively short period of the cell cycle. It alternates with the much longer interphase, where the cell prepares itself for division.

Phases of interphase:

Interphase is divided into the three phases.

  1. G1 (first gap)
  2. S(synthesis)
  • G2(second gap)
  1. G1 phase:

After its production, a cell starts its cell cycle in G1 phase. During this phase, the cell increase its supply of proteins, increases the number of many of its organelles (such as mitochondria, ribosomes), and grows in size. This phase is also marked by the synthesis of various enzymes that are required in the next phase i.e. S phase for DNA replication. Cells that have temporarily or permanently stopped dividing are said to have entered a state of quiescence called G0 phase.

  1. S phase:

In this phase the cell duplicates its chromosomes. The DNA molecule of each chromosome is copied, and new protein molecules are attached. The result is that each chromosome consists of two sister chromatids, which contain identical genes.

  1. G2 phase:

In the G2 phase the cell prepares proteins that are essential for mitosis, mainly for the production of spindle fibres.

After the G2 phase of interphase, the cell enters the division phase i.e. M phase. It is characterized by mitosis, in which the cell divides into the two daughter cells.

G0 phase:

In multicellular eukaryotes, cells enter the G0 state from G1 and may remain quiescent for long periods of time, possibly indefinitely (as is often the case for neurons). Some cell types in mature organism, such as some cells of the liver and kidney, enter the G0 phase semi-permanently and can only be induced to begin dividing under very specific circumstances. Other cells, such as epithelial cells, such as epithelial cells, do not enter G0 and continue to divide throughout an organism’s life.

The events of cell cycle are ordered and directional i.e. each event occurs in a sequential fashion and it is impossible to “reserve” the cycles.

  1. Define mitosis?

Ans. Mitosis:

Mitosis is the type of cell division in which a cell divides into two daughter cells, each with the genetic equivalent of the parent cell i.e. same number of chromosomes as were present in the parent cell.

Because each resultant daughter cell should be genetically identical to the parent cell, the parent cell must make a copy of each chromosome before mitosis. This occurs during S phase to interphase.

  1. Make a list of the events of mitosis. Describe each phase with labeled diagrams?

Ans. Mitosis occurs exclusively in eukaryotic cells. In multicellular organisms, the somatic cells undergo mitosis.

Prokaryotic cells undergo a process similar to mitosis called binary fission. However, prokaryotes cannot be properly said to undergo mitosis because they lack a nucleus and only have a single chromosomes with no centromere.

Phases of mitosis:

A German biologist, Walther Fleming in the 1880’s, gave the detailed account of the stages of cell divisions. He observed that in a dividing cell the nucleus passes through a series of changes which he called mitosis.

The process of mitosis is complex and highly regulated. The sequence of events is divided into major phases:

  1. Kayokinesis:

The division of the nucleus is known as Kayokinesis.

  1. Cytokinesis:

The division of the cytoplasm known as cytokinesis.

  1. Karyokinesis:

The division of the nucleus is further divided into four phases:

  1. Prophase
  2. Metaphase
  • Anaphase
  1. Telophase
  2. Prophase:

Normally, the genetic material in the nucleus is in a loose thread-like form called chromatin. At the onset of prophase, chromatin condenses into highly ordered structures called chromosomes. Since the genetic material has already chromosome has kinetochore at the centromere. A kinetochore is a complex protein structure that is the point where spindle fibers attach.

Close to the nucleus are two centrioles, collectively called a centrosome. Each centriole replicates and thus two daughter centrosomes are formed. Each daughter centrosome acts as coordinating center of the cell’s microtubules.

The two centrosomes give rise to microtubules by polymerizing joining monomers to form polymers the tubulin proteins present in the cytoplasm. The microtubules thus formed are called spindle fibers, and the complete set of the spindle fibers is known mitotic spindle.

During the formation of mitotic spindle, the centrosomes migrate to opposite side of the nucleus. The nucleus and the nuclear envelope have degraded, and spindle fibers have invaded the central space.

In highly vacuolated plant cells, the nucleus has to migrate into the center of the cell before prophase.

The cells of plants lack centrioles. Instead, spindle fibers are formed by the aggregation of tubulin proteins on the surface of the nuclear envelope during prophase.

  1. Metaphase:

When the spindle grows to sufficient length, some of the spindle fibers, known as kinetochore fibres, begin searching for kinetochores to attach. When kinetochore fibers attach to kinetochore, the centromeres of the chromosomes arrange themselves along the equator of the cell forming a metaphase plate.

A number of other fibers (nonkinetochore) interact with the corresponding fibres form the opposite centrosome.

  1. Anaphase:

When a kinetochore spindle fiber connects with the kinetochore of the chromosomes, it starts to pull towards the originating centrosomes. The pulling force dividing the chromosome’s sister chromatids, allowing them to separate. These sister chromatids are now sister chromosomes, and they are pulled apart by shortening of the kinetochore spindle fibres toward the respective centrosomes.

Next, the other spindle fibres (without kinetochore) elongate, pushing the centrosomes and the sets of chromosomes apart to opposite ends of the cell. At the end of anaphase, the cell has successful in separating identical copies of the genetic material into two distinct groups.

  1. Telophase:

Telophase is a reversal of prophase. A new nuclear envelope forms around each set of separated sister chromosomes. Both sets of chromosomes, now surrounded by new nuclear envelopes, unfold back into chromatin.

Nuclear division is complete, but cell division has yet one more step to complete.

  1. Cytokinesis:

Cytokinesis is the division of the cytoplasm.

Cytokinesis in Animal cells:

In animal cells, cytokinesis occurs by a process known as cleavage. A cleavage furrow develops where the metaphase plate used to be. At the site of the furrow, the cytoplasm has a ring of microfilaments (a part of the cytoskeleton). Their ring contracts deepening the furrow and eventually pinching the parent cell into two.

Cytokinesis in plant cells:

Cytokinesis in plant cells occurs differently. Vesicles derived from the Golgi apparatus move to the middle of the cell and fuse to form a membrane- bounded disc called the cell plate or Phragmoplast. The plate grows outward and more vesicle fuse with it. Finally, the membranes of the cell plate fuse with the plasma membrane and its contents join the parental cell wall. The result is two daughter cells, each bounded by its own plasma membrane and cell wall.

  1. Significance of mitosis?

Ans. The importance of mitosis is the maintenance of the chromosomal set i.e. each daughter cell receive chromosomes that are alike in composition and equal in number to the chromosomes of the parent cell.

Following are the occasions in the lives of organisms where mitosis happens.

Development and growth:

The number of cells within an organism increases by mitosis and this is the basis of development from a single cell zygote to the multicellular body and the growth.

Cell replacement:

Cells are constantly sloughed off, dying and being replaced by new ones in the skin and digestive tract. When damaged tissues are repaired, the new cells must be exact copies of the cells being replaced so as the retain normal function of cells. Similarly red blood cells have short life spans of about 4 months and need to be replaced constantly by mitosis.


Some organisms can regenerate parts of the body, and production of new cells is achieved by mitosis. For example, sea star regenerates its lost arm through mitosis.

Asexual reproduction:

Some organisms produce genetically similar offspring. Mitosis is a means for asexual reproduction. For example, hydra reproduces asexually by budding. During this process mitosis forms a mass of cells called bud on the surface of hydra. The mitosis continues in the cells of the bud and it grows into a new individual. The same happened during asexual reproduction (vegetable propagation) in plants.

  1. What do you meant by open or closed mitosis?

Ans. In common mitosis, nuclear envelope disappears and spindles are formed inside the cytoplasm. It is called “open mitosis”.

Fungi and some protists undergo a variation called “closed mitosis” where the spindle forms inside the nucleus.

  1. Write a note on errors in mitosis?

Ans. Errors in mitosis:

Although errors in mitosis are rare, the process may go wrong, especially during early cell divisions in the zygote. For example, during the anaphase of mitosis, a chromosome may fail to separate. One daughter cell will receive both sister chromosomes and the other will receive none. Occasionally, chromosomes may be damaged during mitosis. An arm of the chromosomes may be broken and may incorrectly reattach to another or the original chromosomes, but in reverse orientation. The effect may range from no noticeable effect to cancer induction or organism death.

Errors in the control of mitosis may cause cancer. All cells have genes that control the timing and number of mitosis. Sometimes mutations occur in such genes and the cells continue to divide. It results in growths of abnormal cells called tumors.

As long as these tumors remain in their original location, they are called benign. But if they invade other tissues, they are called malignant (cancerous) and their cells are called cancer cells. Such tumors can send the cancer cells to other parts in the body where new tumors may form. This phenomenon is called metastasis (spreading of diseases).

Nucleus is visible only in interphase while chromosomes are only visible in cell division stage.

  1. Define meiosis. Describe the events that occur during the phases of meiosis?

Ans. Meiosis:

Meiosis is the process by which one diploid eukaryotic cell divides to generate four haploid daughter cells. Diploid means the cells in which chromosomes are in pairs (homologous pairs) while haploid means the cell with half the number of chromosomes i.e. chromosomes are not in the form of pairs.

Phases of meiosis:

Meiosis was discovered and describe for the first time in 1876, by a German biologist Oscar hertwig.

Interphase of a parent cell is followed by meiosis I and meiosis II.

Meiosis I:

The Karyokinesis of meiosis I is subdivided into four phases:

  1. Prophase I
  2. Metaphase I
  • Anaphase I
  1. Telophase I
  2. Prophase I:

Prophase I is the longest phase in meiosis. During this stage, individual chromosomes begin to condense with nucleus. Then the homologous chromosomes line up with each other and from pairs. The combined homologous chromosomes are said to be bivalent. They may also be referred to as a tetrad, a reference to the four sister chromatids.

The two non-sister chromatids of homologous chromosomes become “zipped” together, forming complexes known as synapsis.

In the next stage, the non-sister chromatids of homologous chromosomes randomly exchange their segments and the phenomenon is known as crossing over. The exchange of segments results in a recombination of genetic information.

After crossing over the homologous chromosomes separate from one another. However, they remain tightly bound at chiasmata, the regions where crossing over occurred.

Chromosomes condense further, the nucleoli disappear, and the nuclear envelope disintegrates. Centrioles, which were duplicated during interphase, migrate to the two poles of the cell. They give rise to spindle chromosomes. While the non-kinetochore spindle fibres from both sides interact with each other. There are two kinetochores on each tetrad, one for each kinetochore spindle fiber.

  1. Metaphase I:

As kinetochore spindle fibers from both centrioles attach to their respective kinetochore, the homologous chromosomes align along an equatorial plane forming the metaphase plate.

  1. Anaphase I:

Kinetochore spindle shorten, breaking the chiasmata and pulling homologous chromosomes apart. Since each chromosomes only has one kinetochore, one chromosome is pulled toward one pole, forming two diploid sets. Each chromosome still contains a pair of sister chromatids.

  1. Telophase I:

The first meiotic division ends when the chromosomes arrive at the poles. Each pole now had half the number of chromosomes but each chromosome still consists of a pair of chromatids. The spindle network disappears, and a new nuclear envelopes surrounds each haploid set. They chromosomes uncoil back into chromatin. Cytokinesis, the pinching of the cell in plant cells, occurs, completing the creation of two daughter cells.

After meiosis I both haploid daughter cells enter a period of rest known as interkinesis or interphase II. The interphase II is different from the interphase of mitosis and meiosis I. There is no S-phase and so on DNA replication occurs during this stage.

During crossing over, genetic material is exchanged between sister/non-sister chromatids of homologous/ non-homologous chromosomes.

Meiosis II:

It is the second part of the meiotic process. Much of this part is similar to mitosis. It is subdivided into:

  1. Prophase II
  2. Metaphase II
  • Anaphase II
  1. Telophase II

Prophase II takes much less time compare to prophase I. in this prophase the nucleoli and the nuclear envelope disappear and the chromatin condenses. Centrioles move to the Polar Regions and make spindle fibres.

In metaphase II, the chromosomes attach with the kinetochore spindle fibres and align at the equator of the cell.

This is followed by anaphase II, where the centromeres are cleaved and sister chromatids are pulled apart. The sister chromatids are now called sister chromosomes, and they are pulled toward opposing poles.

The telophase II is marked with uncoiling and disappearance of the chromosomes. Nuclear envelopes reform; cleavage or cell wall formation eventually produces a total of 4 daughter cells, each with haploid set of chromosomes.

  1. Describe the significance of meiosis?

Ans. Significance of meiosis:

The significance of meiosis for reproduction and inheritance was described in 1890 by German biologist. August Weisman, who noted that meiosis was necessary to transform one diploid cell into four haploid cells if the number of chromosomes had to be maintained.

Meiosis is essential for sexual reproduction and therefore occurs in all eukaryotes, including single-called organisms that reproduce sexually. Meiosis does not occur in archaea or prokaryotes, which reproduce asexually by binary fission. Humans, for example, are diploid creatures. The diploid gamete-mother cells undergo meiosis to produce haploid gametes, which are spermatozoa in males and ova in females. These gametes then fertilize, producing a diploid zygote. The zygote undergoes repeated mitosis and develops into the new organism.

Many fungi and many protozoa are haploid. Such organism produce haploid gametes through mitosis. When two gametes fuse they form diploid zygote, which undergoes meiosis immediately, creating four haploid cells. These cells undergo mitosis to create the haploid organism.

Plants’ life cycle shows alternation of generations. The cells of the diploid sporophyte generation undergo meiosis to produce haploid spores, which grow into haploid gametophyte generation. The haploid gametophyte generation produces the diploid zygote. The zygote undergoes repeated mitosis to become the diploid sporophyte.

Because the chromosomes of each parent undergo genetic recombination during, meiosis, each gamete, and thus each zygote, will have a unique genetic makeup. In other words, meiosis and sexual reproduction produce genetic variation. The meiosis allows species to bring variations to handle the change in the environment.

  1. Write a note on errors in meiosis.

Ans. Errors in meiosis:

The normal separation of chromosomes or sister chromatids in meiosis is termed as disjunction. When the separation is not normal, it is called nondisjunction. This results in the production of gametes which have either more or less than the usual number of chromosomes i.e. there may be trisomy (2n+1) or monosomy (2n-1).

It causes several medical conditions in human such as; Down’s syndrome (trisomy of chromosome 21), Kinefelter’s Syndrome (an extra X chromosome in males), and Turner’s syndrome (only one X chromosome present in females). Such individuals have 45 or 57 chromosomes.

  1. Contrast mitosis and meiosis, emphasizing the events that lead different outcomes?

Ans.                       Comparison between mitosis and meiosis


  1. Mitosis takes place in somatic cells.
  2. Mitosis results in two daughter cells.
  • No crossing over takes place.
  1. Number of chromosomes remains same as in parent cell.
  2. Daughter cells remain diploid.


  1. Meiosis takes place in gonals.
  2. Meiosis results in four daughter cells.
  • Crossing over between homologous chromosomes takes place.
  1. Number of chromosomes reduces to half as compared to the parent cell.
  2. Daughter cells become haploid from diploid parent cell.
  3. Write notes on Apoptosis & Necrosis?

Ans. Apoptosis and necrosis are two phenomena of cell death.

  1. Apoptosis:

Apoptosis is one of the main types of programmed cell death, and involves a series of biochemical events. This process is controlled by extracellular signals (e.g. hormones) or intracellular signals (e.g. food deprivation, viral infection).

Following is the series of event in apoptosis.

  1. Cell shrinks and becomes rounded due to the breakdown of the cytoskeleton by enzymes.
  2. The cytoplasm appears dense, and the organelles appear tightly packed.
  • Chromatin undergoes condensation into compact patches against the nuclear envelope.
  1. The nuclear envelope breaks and the DNA is fragmented. Thus, the nucleus breaks into several discrete chromatin bodies.
  2. The cell membrane shows irregular buds known as blebs, through which the cellular components are discharged.
  3. The blebs break off from the cells and are now called apoptotic bodies, which are then phagocytosed by the other cells.

Between 50 billion and 70 billion cells die each day due to apoptosis in an adult human.


Apoptosis can occur when a cell is damaged, infected with a virus, or undergoing stress conditions such as starvation. DNA damage from ionizing radiation or toxic chemicals can also induce apoptosis. The “decision” for apoptosis can come from the cell itself or from the surrounding tissue.

Apoptosis removes the damaged cell, preventing it from getting further nutrients from the organism, nutrients from the organism, or to prevent the spread of viral infection. Apoptosis generally gives advantage during an organism’s life cycle. For example, the differentiation of fingers and toss in a developing human embryo requires cells between the fingers to initiate apoptosis so that the digits can separate.

In the adult organism, the number of cells is kept relatively constant through cell death and division. Cells must be replaced when they become diseased or malfunctioning.

  1. Necrosis:

Necrosis is the name given to accidental death of cells and living tissue. Necrosis is les sequential than apoptosis. There are many causes of necrosis including injury, infection, cancer, infarction, toxins and inflammation.

Necrosis is accompanied by the release of special enzymes from the lysosomes. The lysosomal enzymes break cellular components and may also be released outside the cell to break other surrounding cells. Cells that die by necrosis may also release harmful chemicals that damage other cells. There are many distinctive patterns of necrosis e.g.

  1. Necrosis may occur when a cell is given hypoxic (with less oxygen) environment.
  2. Necrosis be usually associated with cellular destruction and pus formation (e.g. pneumonia).
  • Necrosis may be due to blockage of the venous drainage of an organ or tissue.

Ch#6          ENZYMES

Q.1. Tick the correct answer.                                
1. What is true about enzymes?
(a) They make biochemical reactions to proceed spontaneously (b) They lower the activation energy of a reaction (c) They are not very specific in their choice of substrates (d) They are needed in large quantities
2. To what category of molecules do enzymes belong?
(a) Carbohydrates (b) Lipids (c) Nucleic acids (d) Proteins
3. What is true about cofactors?
(a) Break hydrogen bonds in proteins (b) Help facilitate enzyme activity (c) Increase activation energy (d) Are composed of proteins
4. Prosthetic groups are?
(a) Required by all enzymes (b) Loosely attached with enzymes (c) Proteins in nature (d) Tightly bound to enzyme
5. When we add more substrate to an already occurring enzymatic reaction and there is no increase in the rate of reaction, what would you predict?
(a) All active site have been occupied by substrate molecules (b) The enzymes molecule have denatured (c) More substrate acted an inhibitor (d) More substrate has distributed the pH of the medium
6. Prior to cell division, each chromosome replicates or duplicates its genetic material. The products are connected by a centromere and are called?
(a) Sister chromosomes (b) Homologous chromosomes (c) Sex chromosomes (d) Sister chromatids
7. Enzymes, used in dish washing to remove resistant starch resides, is called?
(a) Amylase (b) Protease (c) Lipase (d) All of these
8. Enzymes get denatured at?
(a) (b) (c) (d)
9. The number of known enzymes is?
(a) 50 (b) 1000 (c) 2000 (d) 2500
10. Include fit model of enzyme activity was proposed by?
(a) Koshland (a) Emil fisher (a) Kohne (a) Mendal
11. The substance on which enzyme works is called?
(a) Substrate (a) Enzyme-substrate-complex (a) Product (a) Coenzyme
12. When all the active sites of the enzymes are occupied (at high substrate concentration), any more substrate molecules do not find free active sites. This state is called?
(a) Enzyme correlation (a) Saturation of substrate (a) Enzyme inhibition (a) Saturation of active sites
13. Which of the following is a coenzyme?
(a) Riboflavin (a) Thiamine (a) Folic acid (a) All of these



Q2. Answers the following short questions.

  1. Define anabolism?

Ans. Anabolism is the total series of chemical reactions involved in the synthesis of compounds.

  1. What are enzymes?

Ans. Enzymes are proteins that catalyze (i.e. speed up) biochemical reactions and are not changed during the reaction. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, the product.

  1. How enzymes lower down the activation energy?

Ans. Enzymes lower the activation energy in several days. They do so by; altering the shape of the substrates and reducing the amount of energy required to complete the transition. Disrupting the charge distribution. Bringing substrates in the correct orientation to react.

  1. What is the use of enzymes in brewing industry?

Ans. Enzymes degrade starch and proteins to produce simple sugars and amino acids that are used by yeast for fermentation (to produce alcohol).

  1. What do you meant by denaturation of enzymes?

Ans. When temperature is raised well above the optimum temperature, the heat energy increases the vibrations of atoms of enzyme molecules and the globular structure of enzymes is lost. This is known as denaturation of enzyme.

  1. What is the effect of pH on enzyme activity?

Ans. All enzymes work at their maximum rate at a narrow range of pH, called as the optimum pH. A slight change (increase or decrease) in this pH causes retardation in enzyme activity or blocks it completely.

  1. Define enzyme-substrate-complex?

Ans. When enzyme attaches with the substrate, a temporary enzyme-substrate (ES) complex is formed. The enzyme catalyzes the reaction and substrate is transformed into product. The ES complex breaks and enzymes and product are released.

  1. Describe lock and key hypothesis of enzyme action?

Ans. According to this model both the enzyme and the substrate possess specific complementary geometric shapes that fit exactly into one another. This model explains enzyme specificity.

  1. Explain induced fit model of enzyme action?

Ans. According to this model:

Enzymes are flexible structures and their active site is reshaped as the substrate with the enzyme. According to this model the active site is not a rigid structure rather it is molded into the precise position to perform its function.

  1. What determines the specificity of enzyme activity?

Ans. The specificity of different enzymes is determined by the shapes of their active sites. The active sites possess specific geometric shapes that fit with specific substrates.

Q3. Answer the following long questions.

  1. Define metabolism and explain its types?

Ans. Metabolism:

The term metabolism is derived from a Greek word meaning “change”. Concept of metabolism was first of all given by Ibn-e-Nafees who stated that “the body and its parts are always undergoing change.”

Metabolism is the set of biochemical reactions that occur in living organisms is order to maintain life. The processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Biochemical reactions in living organisms are essentially energy transfers. During metabolism chemicals are transformed form one form to the other by enzymes.

Types of metabolism:

Metabolism is of two types:

  1. Anabolism:

It is the total series of chemicals reactions involved in the synthesis of compounds.

  1. Catabolism:

Energy is released in catabolism and some of it can be utilized for anabolism. Products of catabolism can be reassembled by anabolic processes into new molecules.

  1. How would you define enzymes? Also describe their characteristics?

Ans. Enzymes:

Enzymes are proteins that catalyze (i.e. speed up) biochemical reactions and are not changed during the reaction.

Enzymes are crucial to metabolism because they act as biocatalysts and speed up and regulate the metabolic pathways.


In enzymatic reactions, the molecules at the beginning of the process are called substrates.


The enzyme converts them into different molecules, the product. Almost all processes in a cell need enzymes in order to occur at significant rates.

Enzymes and activation energy:

All chemicals reactions require energy to break chemical bonds and begin the reaction. The need for activation energy acts as a barrier to the beginning of reaction. Enzymes lower such barriers by decreasing the requirement of activation energy. Thus, in the presence of enzymes, reactions proceed at a faster rate.

Methods of lowering activation energy:

Enzymes lower the activation energy in several ways. They do so by;

  1. Altering the shape of the substrates and reducing the amount of energy required to complete the transition.
  2. Disrupting the charge distribution.
  • Bringing substrates in the correct orientation to react.

Characteristics of enzymes:

In 1878, German physiologist Winhelm Kuhne first used the term enzyme.

  1. Enzymes are globular proteins and range from 62 to over 2,500 amino acids.
  2. Like all proteins, enzymes are made of long, linear chains of amino acids that fold to produce a three-dimensional molecule.
  • Almost all enzymes are protein i.e. hey are made of amino acids.
  1. Most enzymes reactions rates are millions of times faster than those of comparable uncatalyzed reactions.
  2. Enzymes are not consumed by the reactions they catalyze.
  3. Enzymes are usually very specific for the type of reaction and for the nature of their substrates.
  • The activities of enzymes are determined by a small portion of the enzyme molecule (around 34 amino acids) which is directly involved in catalysis. They catalytic region, known as the active site, recognize and binds the substrates, and then carries out the reaction.
  • Since enzymes are extremely selective for their substrates and speed up only a few reactions, the set of enzymes made in a cell determines which metabolic pathways occur in that cell.
  1. Enzymes can be intracellular enzymes (e.g. enzymes of glycolysis working in the cytoplasm) or may be extracellular enzymes (e.g. pepsin enzyme working in the stomach cavity).
  2. The enzymes activity is controlled in the cell by many ways. Enzyme production can be enhanced or diminished by a cell in response to changes in the cell’s environment.
  3. Enzyme activity can also be regulated by inhibitors and activators.
  • Some enzymes do not need any additional components to show full activity. However, others require non-protein molecules or ions called cofactors for activity. Cofactors can be either inorganic (e.g. metal ions) or organic (e.g. Flavin and heme). If organic cofactors are tightly bound to enzyme they are called prosthetic groups, but if they are loosely attached with enzyme, they are called coenzymes. Coenzymes are small organic molecules that transport chemical groups from one enzyme to another. Some important coenzyme are vitamins (e.g. riboflavin, thiamine and folic acid).
  • Several enzymes can work together in a specific order, creating metabolic pathways. In a metabolic pathway, one enzyme takes the product of another enzymes as a substrate. After the catalytic reaction, the product is the passed on to another enzyme.
  1. Write a short note on extensive use of enzymes in industries?

Ans. Uses of enzymes in industry:

Enzymes are extensively used in different industries for fast chemical reactions, for example.

  1. Food industry:

Enzymes that increase sugar molecules form starch are used in production of white bread, buns, and rolls. Enzymes are also used for the production of cheese.

  1. Brewing industry:

Enzymes degrade starch and proteins to produce simple sugars and amino acids that are used by yeast for fermentation (to produce alcohol).

  • Paper industry:

Enzymes degrade starch to lower its viscosity that aids in making paper.

  1. Biological detergent:

Proteases are used for the removal of protein stains from clothes. Amylase enzymes are used in dish washing to remove resistant starch residues.

  1. Briefly describe the factors that affect the activity of enzymes?

Ans. Factors affecting the rate of enzyme action:

Enzymes are very sensitive to the environment in which they work. The activity of an enzyme is affected by any change in conditions that alters its chemistry and its shape. Some of the factors that can affect the rate of enzyme action are being discussed below.

  1. Temperature:

Increases in temperature will speed up the rate of enzyme catalyzed reactions, but only to a point. Every enzyme works at its maximum rate at a specific temperature called as the optimum temperature for that enzyme. When temperature rises to a certain limit, the heat adds in the activation energy and also provides kinetic energy and so reactions accelerated.

But when temperature is raised well above the optimum temperature, the heat energy increases the vibrations of atoms of enzyme molecules and the globular structure of enzymes is lost. This is known as denaturation of enzyme. If results in a rapid decrease in the rate of enzyme action and it may be blocked completely. The optimum temperature for the maximum working speed of human enzymes is .

  1. Substrate concentration:

If there are enzyme molecules with vacant active sites, an increase in substrate concentration will increase the rate of reaction. If the enzyme concentration is kept constant and the amount of substrate is increased, a point is reached where any further increase in substrate does not increase the rate of reaction any more. When all he active sites of the enzymes are occupied (at high substrate concentration), any more substrate molecules do not find free active sites. This state is called saturation of active sites and reactions rate does not increase.

  1. pH:

All enzymes work at their maximum rate at a narrow range of pH, called as the optimum pH. A slight change (increase or decrease) in this pH causes retardation in enzyme activity or blocks it completely.

Every enzyme has its specific optimum pH value. For example pepsin (working in stomach) is active in acidic medium (low pH) while trypsin (working in small intestine) shows its activity in alkaline medium (high pH), change in pH can affect the ionization of the amino acids at the active site.

  1. Describe the lock and key mechanism of enzyme action?

Ans. Mechanism of enzyme action:

In order to explain the mechanism of enzyme action a German chemist Emil Fischer, in 1984, proposed the lock and key model. According to this model both the enzyme and the substrate possess specific. Complementary geometric shapes that fit exactly into one another. This model explains enzyme specificity.

When enzyme attaches with the substrate, a temporary enzyme-substrate (ES) complex is formed. The enzyme catalyzes the reactions and substrate is transformed into product. The ES complex breaks and enzymes and product are released.

  1. Write a short note on “Induced fit Model’?

Ans. The “induced fir model” is more acceptable than the “lock and key”. In 1958 and American biologist Daniel Koshland suggested a modification to the lock and key model and proposed the induced-fit model. He said that enzymes are flexible structures and their active site is reshaped as the substrate with the enzyme. According to this model the active site is not a rigid structure rather it is molded into the precise position to perform its function.

  1. What characteristics of enzyme make them specific for substrates?

Ans. Specificity of enzymes:

There are over 2000 known enzymes, each of which is involved in one specific chemical reaction. Enzymes are also substrate specific. The enzyme protease (which breaks peptide bonds in proteins) will not work on starch (which is broken down by an enzyme amylase). Similarly lipase enzyme acts only on lipids and digests them into fatty acids and glycerol.

The specificity of different enzymes is determined by the shapes of their active sites. The active sites possess specific geometric shapes that fit with specific substrates.

Ch#7                    BIOENERGETICS

Q.1. Tick the correct answer.                                
1. In which of the following steps of respiration is produced?
(a) Glycolysis (b) Krebs cycle (c) Electron transport chain (d) All of these
2. Oxygen takes part in aerobic respiration in?
(a) Glycolysis (b) Link step between glycolysis and Krebs cycle (c) Krebs cycle (d) Electron transport chain
3. When a plant was kept in darkness for many days its leaves turned yellow. Why?
(a) Leaves could not get oxygen and so there was no photosynthesis (b) Leaves could not get light and so there was no respiration (c) Leaves could not get oxygen and so there was no respiration (d) Leaves could not get light and so there was no photosynthesis
4. From which bonds of ATP molecule energy is taken?
(a) P-P bonds (b) C-H bonds (c) C-N bonds (d) C-O bonds
5. In which component of the lead cells, chlorophyll is present?
(a) Stroma (b) Thylakoids (c) Plasma membrane (d) Cytoplasm
6. Which of these can enter into Krebs cycle?
(a) Glucose (b) Pyruvic cycle (c) Citric acid (d) Acetyl Co-A
7. When we work hard we suffer from muscle fatigue because muscle cells?
(a) Carry out aerobic respiration at faster rate and so are tired (b) Carry out anaerobic respiration and so accumulate more CO2 (c) Carry out anaerobic respiration and so accumulate lactic acid (d) Carry out aerobic respiration at faster rate and so burst
8. How many molecules of  are produced when Krebs cycle operates once?
(a) 1 (b) 2 (c) 3 (d) 6
9. In which of the following metabolic processes, oxidation as well as reduction of molecules occur?
(a) Photosynthesis (b) Respiration (c) Both (d) None of these
10. Chlorophyll pigment absorbs maximum light in wavelength of?
(a) Green and blue (a) Green and red (a) Green only (a) Red and blue



Q2. Answer the following short questions.

  1. Why is it said that all life forms are dependent on photosynthesis?

Ans. Products and byproducts of photosynthesis i.e. glucose and oxygen respectively are the basic essential needs of all the living organisms. So, all the life forms are dependent on photosynthesis.

  1. What structure and phenomena are involved in the intake of carbon dioxide and water by plants?

Ans. Water is absorbed through roots and root hairs by the process of osmosis and is transported to leaves through xylem resells.

  1. In what ways the respiratory energy is used in the body of organisms?

Ans. Energy released during respiration is used in different life activities of sensitivity, such as reproduction, movement, lo commotion, sensitivity, transport of materials across the cell, etc.

  1. What is the importance of anaerobic respiration?

Ans. Anaerobic respiration has been solely used on earth when no oxygen was present on our plant. Many bacteria and fungi still get energy through anaerobic respiration. Human skeletal muscle cells get energy through anaerobic respiration during strenuous exercise when the oxygen supply cannot be increased to fulfill the demand. anaerobic respiration of bacteria and fungi is used for making cheese, yogurt, bread, soy sauce, etc.

Q3. Answer the following long questions.

  1. Why do we need energy? Describe its different forms.

Ans. A living cell exhibits ceaseless chemical activity. Cells are like open system i.e. substances are entering and leaving the cell all the times. Inside cells the substances are broken down and new substances are formed. Energy drives all these processes in a cell.

Forms of energy:

In living organisms energy exists in two forms:

  1. kinetic energy:

Kinetic energy is actively involved in doing work, and potential energy is stored for future use.

  1. Potential energy:

The potential energy is stored in chemical bonds and is released as kinetic energy when these bonds break.

  1. How would you define bioenergetics while relating it to the oxidation reduction reactions in living systems?

Ans. Bioenergetics:

Bioenergetics is the study of energy relationships and energy transformations (conversions) in living organisms.


Organisms obtain energy by metabolizing the food they eat or prepare. The food contains potential energy in its bonds. When these bonds are broken down, a large amount of kinetic energy is usually released. Some of this energy is stored in the form of potential energy in the bonds of ATP molecules while the rest escapes as heat. The potential energy stored in ATP is again transformed into kinetic energy to carry out the life activities.

Oxidation-reduction reactions:

All the activities in living organisms need a constant flow of energy. This energy is used in building, breaking down, assembling, and eliminating substances, which results in the maintenance, growth, and reproduction of organisms.

For all these life processes, oxidation-reduction reactions are the direct source of energy. Oxidation-reduction reactions involve exchange of electrons between atoms.


The loss of electrons is called oxidation.


The gain of electrons is called reduction.

Energy through electrons:

Electrons can be an energy source. It depends upon their location and arrangement in atoms. For example, when they are present in oxygen, they make stable association with oxygen atom and are not good energy source. But if electrons are dragged away from oxygen and attached to some other atom e.g. carbon or hydrogen, they make unstable association. They try move back to oxygen and when this happens, energy is released.

In living organisms redox reactions involve the loss and gain of hydrogen atoms. A hydrogen atom contains one proton and one electron. It means that similarly when a molecule gains hydrogen atom, it actually gains an electron.

  1. Interpret that ATP is the chief energy currency of all cells? Explain the structure and importance of ATP.

Ans. Adenosine Tri Phosphate (ATP):

The major energy currency of all cells is a nucleotide called Adenosine Tri Phosphate (ATP).


ATP was discovered in 1929 by Karl Lohmann and was proposed to be the main energy-transfer molecule in the cell by the Nobel Prize winner, Fritz Lipmann in 1941.


The ability of ATP to store and release energy is due to its molecular structure.

“Molecular structure of adenosine tri phosphate”

Each ATP molecule has three subunits:

  1. Adenine-a double-ringed nitrogenous base
  2. A ribose-a five-carbon sugar
  • Three phosphate groups in a linear chain


The covalent bond connecting two phosphates is indicated by the “tlide ( ) and it is a high-energy bond. The energy in this bond is released as it breaks and inorganic phosphate (Pi) gets separated from ATP. The breaking of one phosphate bond released about 7.3 (7,300 calories) per mole of ATP as follows:

“ATP+  ADP+ ” energy (7.3 kcal/mole)

The energy from ATP is sufficient to drive most of the cell’s energy- requiring reactions. In common energy reactions only the outermost of the two high-energy bonds breaks. When this happens, ATP becomes ADP (adenosine diphosphate) and one Pi is released.

In some cases, ADP is further broken down to AMP (adenosine monophosphate) and Pi as follows:

“ATP+  AMP+ ” energy (7.3 kcal/mole)

Cells constantly recycle ADP by recombining it with  or ATP. The synthesis of ATP from ADP an  requires the expenditure of 7.3 kcal of energy per mole. This energy is obtained from the oxidation of foodstuff. So we can summarize that ATP is generated by energy-releasing processes and is broken down by energy between metabolic reactions.

ATP is the main energy source of majority of the cellular functions like the synthesis of macromolecules (DNA, RNA, and proteins), movement, transmission of nerve impulses, active transport, exocytosis and endocytosis, etc.

ATP plays a central role as energy currency in all organisms it must have appeared in the early history of life.

  1. Define photosynthesis?

Ans. Photosynthesis:

Photosynthesis is an anabolic (building) process and is an important component of bioenergetics in living systems.

Autotrophic organisms use inorganic raw materials such as carbon dioxide and water for the preparation of organic food, which primarily comprises carbohydrates. The organic food thus prepared may be used for getting energy or may be converted to other forms such as protein, lipids etc.


Photosynthesis is the synthesis of glucose from carbon dioxide and water in the presence of sunlight (and chlorophyll), with oxygen as a by-product. It is the most important biochemical pathway and nearly all life depends on it. In this process the energy-poor inorganic oxidized compounds of carbon (i.e. ) are reduce to energy-rich carbohydrates i.e. glucose. It comprises many coordinated biochemical reactions that occur in plants, some protists (algae), and some bacteria.

“6 +12 + photons +

“Carbon dioxide+ water+ light energy+ glucose+ oxygen+ water

  1. What structure and phenomena are involved in the intake of carbon dioxide and water by plants?

Ans. Intake of Carbon dioxide and water:

Water and salts are absorbed by the root hairs, which provide the larger surface areas for this absorption. The sap present in the root hairs is more concentrated (contains more salts) as compared to the dilute solution (containing less salts) present in surrounding soil. Thus water enters from the soil into the root hairs by osmosis thus diluting their sap as compared to the inner cells of the root. In this way water enters in the inner cells of the root and eventually reaches xylem vessels. The xylem vessels transport water to the leaves using the force of transpiration pull.

Intake of Carbon Dioxide:

The air that enters the leaf through tiny pores (stomata) diffuses into the air spaces present around mesophyll cells. This air carries  which gets absorbed in the thin layer of water surrounding the mesophyll cells. From here the carbon dioxide diffuses into the mesophyll cells.

Stomata cover only 1-2% of the leaf surface but they allow much gas to diffuse through them.

  1. Explain the mechanism of photosynthesis with the help of light and dark reaction?

Ans. Mechanism of photosynthesis:

Photosynthesis occurs in two phases.

Light reactions:

During the first phase, light energy is captured and is used to make high-energy molecules (ATP and NADPH). These reactions, which are known as light reaction, take place on the thylakoid membranes of chloroplasts.

Dark reactions:

During the second phase, carbon dioxide is reduced to make glucose. The energy in the form of ATP is utilized in this process and is then stored in the bonds of glucose. Since these reactions do not use light directly, they are known as dark reactions. The dark reactions take place in the stroma of the chloroplasts.

Light reactions:

The events of light reactions are as follows:

  1. When chlorophyll molecules absorb light, their energy level boosts and their electrons are emitted.
  2. Electrons are passed to electron transport chains to produce ATP.
  • Light also breaks water molecule (photolysis) and oxygen is released. The hydrogen atoms of water give electrons to chlorophyll and becomes ions.
  1. The electrons of chlorophyll, after the production of ATP, and the hydrogen ions of water are used for the reduction NADP’ into the NADPH.

The whole series of reactions is called as Z-scheme due to its Z-shaped flow chart.

Dark reactions (Calvin Cycle):

Dark reactions occur as readily in the because of light as in its presence, as long as ATP and NADP are available. The details of dark reactions were discovered by Melvin Calvin and his colleagues at the University of California. Calvin was awarded Nobel Prize, in 1961, for his work on the photosynthesis.

The summary of the events of dark reactions, also known as Calvin Cycle is as follows:

  1. Molecules are combined with 5-carbon compounds to form temporary 6-carbon compounds, each of which splits into two 3-carbon compounds.
  2. The 3-carbon compounds are reduced to 3-carbon carbohydrates by using ATP and hydrogen from NADPH. The 3-carbon carbohydrates are used to manufacture glucose.
  • The 3-carbon carbohydrates are also used to regenerate the original 5-carbon compound.
  1. What is the role of chlorophyll and light in photosynthesis?

Ans. Role of Chlorophyll and light:

Sunlight energy is absorbed by chlorophyll. It is then converted into chemical energy, which drives the photosynthetic process. Not all the light falling on the leaves is absorbed. Only about one percent of the light falling on the leaf surface is absorbed, the rest is reflected or transmitted.

The light rays of different wavelengths are not only differently absorbed by photosynthetic pigments but are also differently effective in photosynthesis. Pigments are the substrates that absorb visible light. Different pigments absorb light of different wavelengths (colors).

When chlorophyll absorbs light, its electrons are excited and they leave chlorophyll molecule. The excited electrons are passed through electron transport chain and their energy is captured for the formation of ATP and for reducing NADP to NADPH.

The photosynthetic pigments are organized in the form of clusters, called photosystems in thylakoid membrane of chloroplasts.

Chlorophyll’s is the main photosynthetic pigment. Others are called accessory pigments and include chlorophyll-b and carotenoids.

Chlorophyll absorbs mainly blue and red lights. Some wavelengths not absorbed by chlorophyll ‘a’ are very effectively absorbed by accessory pigments and vice-versa.

  1. Write a comprehensive note on limiting factors in photosynthesis?

Ans. Limiting factors in photosynthesis:

Any environmental factor the absence or deficiency of which of can decrease the rate of a metabolic reaction, is called limiting factor for that particular reaction.

Following factors limit the rate of photosynthesis:

  1. Light intensity:

The rate of photosynthesis varies with light intensity. It decreases as the light intensity decreases and increases as the intensity increases. However at much higher light intensity the rate of photosynthesis become constant.

  1. Temperature:

The rate of photosynthesis decreases with decrease in temperature. It increases as the temperature is increased over a limited range. But if light intensity is low, increasing the temperature has little influence on the rate of photosynthesis.

  1. Carbon dioxide concentration:

As carbon dioxide concentration rises, the rate of photosynthesis goes on increasing with until limited other factors. The initial enzyme of dark reactions, which combines carbon dioxide with 5-carbon compound, has a binding affinity for both carbon dioxide and oxygen.

When the concentration of carbon dioxide is high, the enzyme will capture carbon dioxide. However, if the oxygen concentration is high, it will bind oxygen instead of carbon dioxide and there would be no photosynthesis. Increase in carbon dioxide concentration beyond a threshold level causes the closure of stomata and it decreases and rate of photosynthesis.

  1. Define respiration? Also describe its different types.

Ans. Respiration:

Organisms utilize oxygen for the breakdown of C-H bond present in the food in their cells. This breakdown yields energy which is transformed into ATP. During cells process the C-H bonds are broken by oxidation-reduction reaction and so carbon dioxide and water are also produced. The cellular energy-yielding process is called cellular respiration.

The most common fuel used by the cell to get energy by cellular respiration is glucose. They way glucose is oxidized depends on the availability of oxygen. The cellular respiration occurring in the presence of oxygen is called aerobic respiration while the one that occurs in the absence of oxygen is called anaerobic respiration.

Types of respiration:

There are two types of respiration:

  1. Aerobic respiration
  2. Anaerobic respiration
  3. Aerobic respiration:

In the presence of oxygen, complete oxidation of glucose occurs with maximum release of energy.

It occurs in two phases:

  1. Phase 1:

In the first phase of aerobic respiration, a molecule of glucose (6-C) is broken down into two molecules of pyruvic acid (3-C).

  1. Phase 2:

In the second phase, the molecules of pyruvic acid are completely oxidized (all C-H bonds are broken) to  and water and all the energy is released. The overall reaction is as follows:

+ Energy

Glucose+Oxygen Carbon+Water+Energy dioxide

  1. Anaerobic Respiration (Fermentation):

In the absence of oxygen, glucose is incompletely oxidized with less amount of energy released.

It also occurs in two phases.

Phase 1:

In anaerobic respiration, the first phase is exactly similar to that of aerobic respiration. A molecule of glucose is broken down into two molecules of pyruvic acid.

Phase 2:

          In the second phase, pyruvic acid is not completely oxidized (due to the absence of oxygen). It is transformed into ethyl alcohol or lactic acid. In this way many of the C-H bonds are left unbroken in the products.

Types of Anaerobic respiration:

Anaerobic respiration is further classified as;

  1. Lactic acid fermentation:

It occurs in skeletal muscles of humans and other animals during extreme physical activities when oxygen cannot be transported to the cells as rapidly as it is needed. This also happens in the bacteria present in milk. In this type of anaerobic respiration, each pyruvic acid molecule is converted into lactic acid ( )

2( )+4H 2( )

Pyruvic acid + Hydrogen + Lactic acid

  1. Alcoholic fermentation:

It occurs in bacteria, yeasts, etc. In this type of anaerobic respiration, pyruvic acid is further broken down into alcohol and carbon dioxide.

2( )              +        4H      2( )   +

Pyruvic acid +        Hydrogen     Alcohol        +        Carbon dioxide

  1. What is the importance of anaerobic respiration?

Ans. Importance:

When life evolved on earth, the early land or water habitats did not have and supply of free oxygen. In these anaerobic conditions early organisms respired anaerobically and got energy for their life activities.

Even today when free oxygen is available, some organisms including some bacteria and some fungi get energy from anaerobic respiration and are called anaerobes. It happens when skeletal muscles have to work hard (during exercise etc) but oxygen supply cannot be increased to fulfill the demand.

Scientists have used the fermenting abilities of fungi and bacteria for the benefit of mankind. For examples, the fermenting powers of bacteria are used for making cheese and yogurt.

Fermentation in yeasts is used in brewing and baking industries. Similarly the soy sauce is made through the fermentation by a fungus aspergillus.

  1. Outline the mechanism of respiration while defining Glycolysis, Krebs cycle and electron transport chain?

Ans. Mechanism of respiration:

The process of respiration involves complex series of reactions. For the study of all the reactions of glucose oxidation, we will go into the mechanism of aerobic respiration.

Aerobic respiration is a continuous process, but for convenience we can divide it into three main stages:

Site of Glycolysis:

Glycolysis occurs in the cytoplasm and oxygen is not involved at this stage. That is why it occurs in both types of respiration i.e. anaerobic and aerobic.

Site of Krebs cycle and ETC:

Krebs cycle and ETC occur within mitochondria where the presence of oxygen is essential.

  1. Glycolysis:

In glycolysis, glucose is broken into two molecules of pyruvic acid.

  1. Krebs Cycle:

In Krebs cycle, the pyruvic acid molecules are completely oxidized into  and .

Before entering in Krebs cycle, pyruvic acid is changed into a 2-carbon compound called acetyl-CoA.

  1. Electron transport chain:

The final step of cellular respiration is the transfer of electron on a electron transport chain. In this step the energy carried by electrons is used to synthesize ATP.

In electron transport chain NADH and  release electrons and hydrogen ions. These   electrons are taken up by a series of electron carriers. When electrons move through the series of electron carriers they lose energy, which is used to synthesize ATP molecules. At the end of the chain electrons and hydrogen ions combine with molecular oxygen and form water.

  1. Write a note on energy budget of respiration?

Ans. The energy budget of respiration:

Each NADH molecule generated in the link step (between glycolysis and Krebs cycle) and in Krebs cycle produces three ATP molecules in electron transport chain.

While each NADH generated in glycolysis gives profit to two ATP molecules because it has to be transported across the mitochondrial membrane and it costs one ATP.

Each  molecule produces two ATP molecules. The total output of ATPS can be calculated from the following data.

During anaerobic oxidation of a glucose molecule only 2 ATP molecules are gained as the net profit. It is because there is no Krebs cycle and electron transport chain in anaerobic respiration.

  1. Write down the difference between photosynthesis and respiration?

Ans. Difference between photosynthesis and respiration:

Properties Photosynthesis Respiration
Metabolism Anabolism Catabolism
Energy investment/production Investment of light energy to store it in the form of bond energy Bond energy transformed into chemical energy of ATP
Organisms capable of; Some bacteria, all algae all plants All organisms
Site of occurrence Chloroplasts In cytoplasm and mitochondria
Time of occurrence In daytime only, in the presence of light All the time


  1. Draw a comparison of aerobic and anaerobic respiration?

Ans. Comparison of aerobic and anaerobic respiration:

Properties of oxygen Aerobic respiration Anaerobic respiration
Presence of oxygen Yes No
Number of ATP as net profit 36
Final products Lactic acid of ethanol +
Site of occurrence Glycolysis in cytoplasm and Krebs cycle and electron transport chain in mitochondria In cytoplasm
Importance Major source of energy for most organisms Source of energy for anaerobic organisms source of energy for aerobic organisms in short supply of
source of many products (ethanol, cheese etc)


Ch#  8        NUTRITION

Q.1. Tick the correct answer.                                
1. What is the primary nutrient that provides quick useable energy for the body?
(a) Carbohydrates (b) Proteins (c) Lipids (d) Nucleic acids
2. The wave like movement of muscle that pushes food through the digestive system is called?
(a) Chemical digestion (b) Emulsification (c) Absorption (d) Peristalsis
3. Micronutrients of plants are?
(a) Available in the soil only in small amounts (b) Required by plants in small amounts (c) Small molecules required by plants (d) Useful, but not required by plants
4. Which of the following does not occur in the oral cavity?
(a) Lubrication of the food (b) Beginning of protein digestion (c) Breaking the food into small fragments (d) All of the above do occur in the oral cavity
5. Where are the villi found?
(a) Esophagus (b) Stomach (c) Small intestine (d) Large intestine
6. Ulcers occur in the?
(a) Stomach (b) Duodenum (c) Small intestine (d) All of these
7. Which group of enzymes breaks up starches and other carbohydrates?
(a) Proteases (b) Lipases (c) Amylase (d) None of these
8. The pancreas produces digestive enzymes and releases them into the?
(a) Colon (b) Gallbladder (c) Liver (d) Duodenum
9. In the stomach, pepsinogen is converted into?
(a) Pepsin (b) Bicarbonate (c) HCl (d) Gastrin
10. The hepatic portal vein carries blood from the _____ to the ____?
(a) Small intestines, liver (a) Small intestine, heart (a) Liver, heart (a) Small intestine, colon
11. Which of the following is not a function of the liver?
(a) Convert glucose to glycogen (a) Converts glycogen to glucose (a) Detoxifies poisonous substances (a) Produces digestive enzymes
12. The diseases of Kwashiorkor and Marasmus may be due to?
(a) Mineral deficiency (a) Over-take of nutrients (a) Protein-energy malnutrition (a) Ulcer
13. Which food group is our body’s best source of energy?
(a) Meat group (a) Fats, oils and sweets (a) Breads and cereals (a) Milk and cheese



Q2. Answer the following short questions.

  1. What are the health risks if we take more saturated fatty acids in our diet?

Ans. Saturated fatty acids can increase a person’s cholesterol lend, which may eventually result in the clogging of arteries and ultimately heart disease.

  1. How can the deficiency of vitamin A cause blindness?

Ans. As vitamin A combines with a protein called opsin to form rhodopsin in rod cells of retina of eye, its deficiency makes it difficult to see in dim light.

  1. How will you differentiate between bolus and chime?

Ans. Morsel of food mixed with saliva in the oral cavity is called bolus while the morsel of food mixed with gastric juice in stomach is called chime.

  1. Which sphincter play role in the movement of food in and out of stomach?

Ans. Cardiac sphincter (between stomach and oesophagus) and pyloric sphincter (between stomach and duodenum) control the movement of food in and out of stomach.

  1. Stomach is an organ of the digestive system, but it also what function if performs?

Ans. Hormone released by the stomach is gastric. It enters blood and is distributed to body pasts. In stomach, it stimulates the gastric glands to secrete more gastric juice.

Q3. Answer the following long question.

  1. a) Define nutrition and nutrients. Explain why nutrition is essential?
  2. b) Define autotrophic organism and heterotrophic organism?

Ans. Nutrition:

The process in which food is obtained or prepared, absorbed and converted into body substances for growth and energy, is called nutrition.


Nutrients are the elements and compounds that an organism obtains and use as energy source or as components for the synthesis of new materials.

Importance of nutrition:

Nutrition is essential for several purposes.

  1. It constitutes a source of energy for the organism.
  2. It provides building material for growth and development.
  • It regulates various body functions.

Autotrophic organisms:

Autotrophic organisms (some bacteria, all algae, and all plants) obtain water, carbon dioxide and minerals from their environment and prepare their own food which is then used for growth and energy.

Heterotrophic organisms:

Heterotrophic organisms (most bacteria, and all protozoans, fungi and animals) obtain their food from other organisms and use it for growth and energy.

  1. Write a short note on mineral nutrition in plants?

Ans. Mineral nutrition in plants:

Plants require mineral elements for various activities and structures. These required nutrients are categorized in to two groups:

  1. Macronutrients:

The elements which are required by plants in larger quantities are called macronutrients. These are nine in number.

  1. Micronutrients:

The mineral elements which are required in lower quantities are called micronutrients. These are eight in number. Table presents a brief guideline of the role of macro-and micronutrients that are crucial for growth. If any one of these is not supplied, plants display abnormalities of growth and do not reproduce normally.

Macronutrient Role of mineral elements in plant life
Carbon Forms the backbone of many plant biomolecules
Hydrogen Necessary for building biomolecules
Phosphorus Component of ATP, nucleic acids, and coenzymes, necessary for seed germination, photosynthesis, protein formation etc
Potassium Regulates the opening and closing of the stoma, reduces water loss from the leaves
Nitrogen Component of proteins, hormones, chlorophyll, vitamins and enzymes
Sulphur Component of proteins, vitamins and enzymes
Calcium Activates enzymes, is a structural component of cell wall, influences of water movement in cells.


Micronutrient Role of mineral elements in plant life
Iron Necessary for photosynthesis, activates many enzymes
Molybdenum Component of the enzyme that reduces nitrates to ammonia, important in building amino cells
Boron Important in sugar transport, cell division, and synthesizing certain enzymes
Copper Component of several enzymes
Manganese Involved in enzymes activity for photosynthesis, respiration, and nitrogen metabolism
Zinc Required in a large number of enzymes
Chlorine Involved in osmosis of water
Nickel Required in a nitrogen metabolism


  1. What are effects of nitrogen and magnesium ions on plant growth?

Ans. Role of nitrogen:

Plants get nitrogen in the form of nitrates.

  1. Nitrogen is major component of proteins, hormones, chlorophyll, vitamins and enzymes essential for plant life.
  2. Nitrogen metabolism is a major factor in stem and leaf growth.
  • Too much nitrogen can delay flowering and fruiting.
  1. Deficiencies of nitrogen can reduce yields, because yellowing of the leaves and stunt growth.
  2. Carnivorous plants have evolved mechanisms for trapping and digesting small animals. The products of this digestion are used supplements the plant’s supply of nitrogen.

Role of magnesium:

  1. Magnesium is a structural component of chlorophyll molecule.
  2. It is necessary for functioning of plant enzymes to produce carbohydrates, sugars and facts.
  • It is used for fruit and nut formation and essential for germination of seeds.
  1. Deficiency of magnesium causes yellowing and wilting of leaves.
  2. How are the inorganic and organic fertilizers important in agriculture?

Ans. Fertilizers:

Addition of certain minerals to the soil sometimes resulted in plants with desirable characteristics (e.g. more fruit, faster growth, better color, more attractive flowers.) such materials were named as fertilizers.

Fertilizers are broadly classified as:

  1. Inorganic fertilizer:

Naturally occurring inorganic fertilizers include rock phosphate, elemental sulfur, and gypsum that are no chemically modified. If nitrogen is the main element, they are often described as nitrogen fertilizers. Most inorganic fertilizers dissolve readily in water and are immediately available to plants for uptake.

  1. Organic fertilizer:

A natural organic fertilizer is the one that is derived from either plant or animal materials containing one or more essential elements.

Organic fertilizers are more complex chemical substances that take time to be broken down into forms usable by plants root.

However their excessive amounts can cause environmental degradation due to nitrate leaching or run off of soluble organic compounds.

Manure and compost are used as organic fertilizers.

The can also increase soil drainage, aeration, water holding capacity, and the ability of the soil to hold nutrients.

Environmental hazards related to fertilizers use:

  1. The massive quantities of inorganic fertilizers affect the soil nutrient-holding capacity.
  2. Their high solubilities also degrade ecosystems through eutrophication (means an increase in chemical nutrient typically compounds containing nitrogen or phosphorus in ecosystem).
  • Storage and application of some nitrogen fertilizers may cause emission of the greenhouse gas nitrous oxide ( ).
  1. Ammonia gas ( ) may be emitted from the applied inorganic fertilizers. This extra ammonia can also increase soil acidity.
  2. Excessive nitrogen fertilizers can lead to pest problems by increasing their reproduction rate.

For these reasons, it is recommended that the nutrient content of the soil and nutrient requirements of the crop are carefully balanced with application of inorganic fertilizers.

  1. Write a comprehensive note on major components of food?

Ans. The nutritional requirements of human and other animals are relatively extensive and complex as compared with the simple requirements of plants.

Major components of food:

Like other animals, the nutrients used by humans include carbohydrates, lipids, nucleic acids, proteins, minerals, vitamins. Besides these nutrients, they also require water.


Carbohydrates are the basic source of energy for all animals.


Animals get their carbohydrates from their environment (compared with plants, which synthesized carbohydrates during photosynthesis). Human get carbohydrates from the food like bread, pastas, beans, potatoes, bran rice and cereals.


  1. Carbohydrates require less water for their digestion.
  2. About half 2/3 of the total calories every animal consumes daily are from carbohydrates.
  • Glucose is the carbohydrates most often used as an energy source.
  1. It is metabolized during cellular respiration and part of the energy is used to synthesize ATP.
  2. Other useful carbohydrates are maltose, lactose, sucrose, and starch.
  3. Carbohydrates contain 4.0 kilocalories per gram.


The lipids present in food are composed of:

  1. Fatty acids:

The fatty acids of lipids may be of two types:

  1. Saturated fatty acids:

Have all of their carbon atoms bonded to hydrogen atoms.

  1. Unsaturated fatty acids:

Have some of their carbon atoms double-bonded or triple-bonded in place of a hydrogen atoms.


The lipids containing saturated fatty acids are solid at room temperature. For example, butter contains nearly 70% saturated and 30% unsaturated fatty acids. These are called fats.


The lipids containing unsaturated fatty acids are liquid at room temperature. Sunflower oil, on the other hand, contains nearly 75% unsaturated fatty acids. These are called oils.


  1. Lipids are used to from membrane, the sheaths surrounding neurons, and certain hormones.
  2. Lipids are also extremely useful energy sources. One gram of lipids contains 9.0 kilocalories of energy.


Important sources of lipids include milk, butter, cheese, eggs, mutton, fish mustard seeds, coconut, and dry fruits etc.


Proteins are composed of amino acids. The body requires amino acids to produce new body protein and to replace damaged proteins. Amino acids are classified as essential (which we cannot produce) and non-essential (which we can produce from other nitrogen containing compounds) amino acids. Consuming a diet that contains adequate amounts of essential (but also non-essential) amino acids is particularly important.


  1. Proteins are essential components of cytoplasm, membranes and organelles.
  2. They are also the major components of muscles, ligaments, and tendons.
  • Proteins play role as enzymes.
  1. Proteins can also be used for gaining energy.
  2. One gram of proteins contains 4.0 kilocalories of energy.
  3. Proteins can be converted into carbohydrates.


Dietary sources of protein are meat, eggs, grains, legumes, and dairy products such as milk and cheese.


Minerals are inorganic elements that originate in the earth and cannot be made in the body.


The play important roles in various body functions and are necessary to sustain life and maintain optimal health.


Most of the minerals in the human diet come directly from plants and water, or indirectly from animal foods.


Minerals are categorized into major minerals and trace minerals.

Major minerals:

Are those that are required in the amounts of 100mg (milligrams) or more per day, while trace minerals are required in amounts less than 100 mg per day.

The roles of major and minor minerals in human body are given in the table.

Important minerals in human diet and their roles:

Minerals Role in body
Major minerals
Sodium Fluid balance in the body helps in absorption of other nutrients.  


Important for muscle contraction, nerve impulse transmission, heart function, and blood pressure

Potassium Fluid balance in the body acts as cofactor for enzyme
Chloride Fluid balance in the body component of hydrochloric acid
Calcium Development and maintenance of bones and teeth blood clothing
Trace minerals
Iron Oxygen transport storage  

Act as enzyme cofactors support immune function

Zinc Aids insulin action helps in growth and reproduction
Copper Acts as enzyme cofactor
Chromium Helps in insulin action
Fluoride Stabilizes bone mineral and hardens tooth enamel
Iodine Essentially for normal thyroid function


          Minerals, both major and trace, play vital roles in human health. The most common result of mineral deficiency is the poor growth and development in children. Minerals interact with each other and with other nutrients, and caution is required when using supplements, as excess intake of one mineral can lead to the deficiency of another nutrient.

  1. Which foods contain calcium and iron and what role these minerals play in our bodies?

Ans. Role of calcium:

  1. Calcium is essential for the development and maintenance of bones and teeth.
  2. It is also needed for maintaining cell membranes and connective tissues.
  • It is essential for the activation of several enzymes.
  1. Calcium also aids in blood clotting.


Human get calcium from milk, cheese, egg yolk, beans, nuts, cabbage etc.

Deficiency symptoms:

Deficiency of calcium causes spontaneous discharge of nerve impulses which may result in tetany. Bones also become soft, blood clots slowly, and wounds heal slowly.

Role of iron:

  1. Iron plays a major role in oxygen transport and storage.
  2. Iron is a component of haemoglobin in red blood cells and myoglobin in muscle cells.
  • Cellular energy production also requires iron which acts as enzyme cofactor.
  1. Iron also supports immune function.


Humans get iron from red meat, egg yolk, whole wheat, fish, spinach, mustard, etc.

Deficiency symptoms:

Iron deficiency is the most common nutrient deficiency worldwide.

  1. Iron-deficiency causes anemia which effects hundreds of millions of people. Infants, young children, adolescents, and pregnant and lactating women are especially vulnerable due to their high demand for iron.
  2. Write down the importance of vitamin A, C, D in our food?

Ans. Vitamins in food:


Vitamins are chemical compounds that are required in low amount but are essential for normal growth and metabolism.

Vitamins may be divided into two groups:

  1. Fat-soluble vitamins (vitamin A, D, E and K)
  2. Water soluble vitamins (the B vitamins and vitamin C)

Cooking or heating destroys the water-soluble vitamins more readily than the fat-soluble vitamins. Fat-soluble vitamins are much less excreted from the body ad compared to water-soluble vitamins. This means that levels of water-soluble vitamins in the body can become depleted more quickly, leading to a vitamin deficiency.

Vitamin A:

Vitamin A was the first fat-soluble vitamin identified (in 1913). It performs following functions:

  1. Vitamin A combines with a protein called opsin to form rhodopsin in the rod cells of the retina of eye. When vitamin A is inadequate, the lack of rhodopsin makes it difficult see in dim light.
  2. It is involved in normal cell differentiation, a process through which embryonic cells transforms into mature cells with highly specific functions.
  • Vitamin A supports male and female reproductive processes and bone growth.
  1. It is essential for immune function and vitamin- A deficiency causes decreased resistance to infections.


Humans get vitamin A form leafy vegetables (spinach, carrots), yellow/orange fruits (mango), liver, fish, egg, milk, butter etc.

Deficiency symptoms:

Deficiency of vitamin A is the leading cause of blindness is children worldwide.

One of the symptoms of vitamins-A deficiency is night blindness. It is a temporary condition, but if left untreated it can cause permanent blindness.

Vitamin-A deficiency can also cause a condition in which hair follicles become plugged with keratin, giving bumpy appearance rough, dry texture to skin.

Vitamin C(ascorbic acid):

  1. Vitamin C participates in many reactions by donating electrons, essential to the activity of many enzymes.
  2. Vitamin C is needed to form collagen (a fibrous protein) that gives strength to connective tissues.
  • Collagen is also needed for the healing of wounds.
  1. Vitamin C in white blood cells enables the immune system of function properly.


We get vitamin C from citrus fruits (e.g. oranges, lemons, and grape fruit), leafy green vegetables, beef liver etc.

Deficiency symptoms:

Deficiency of vitamin C causes connective tissue changes throughout the body.

The disease known as Scurvy results from lack of vitamin C. In this condition the synthesized collagen is too unstable. Symptoms of scurvy include tiredness, nausea, muscle and joint pain, swollen and bleeding gums, slow wounds healing, and dry skin and hair.

Vitamin D (Calciferol):

  1. The best-known function of vitamin D is to help regulate blood levels of calcium and phosphorus.
  2. Vitamin D increases absorption of these minerals from the intestine an their deposition in bones.


Vitamin D is mainly found in fish liver oil, milk, ghee, and butter etc. it is also synthesized by the skin when ultraviolet (UV) radiation from the sun are used to covert a cholesterol derivative into vitamin D.

Deficiency symptoms:

Long-term deficiency of vitamin D affects the bones. In children, vitamin-D deficiency leads to rickets, a condition in which bones weaken and bow under pressure. In adults vitamin-D deficiency causes osteomalacia, or “soft bone,” increasing the risk for fractures in bones.


Functions Deficiency Sources
Vitamin A Vision in dim light and cell differentiation, growth and immunity Poor growth, night blindness, blindness, dry skin Leafy vegetables (spinach, carrots), yellow/orange fruits fish, liver, egg, milk, and butter
Vitamin C To form collagen, to heal wounds, help in proper functioning of immune system Scurvy, fatigue, poor wound healing, pinpoint hemorrhages around hair follicles, bleeding gums & joints Citrus fruits, leafy green vegetables, and beef liver
Vitamin D Maintenance of intracellular and extracellular calcium concentrations Rickets in children, osteomalacia in adults Fish liver oil milk, ghee, and butter, also synthesized by the skin


  1. Why water and dietary fibre are not considered as nutrients, but they do play important role in life?

Ans. Effects of water and dietary fibre:

Strictly speaking, water and dietary fibre are not considered as nutrients, but they do play important role in life.



Important sources of daily water intake are natural water, milk, juicy, fruits and vegetables.


  1. Approximately 60% of the adult human body is composed of water.
  2. Nearly all of the life-sustaining chemical reactions require an aqueous (water) environment.
  • Water also functions as the environment in which water-soluble foodstuff is absorbed in the.
  1. Intestines and the waste products are eliminated in urine.
  2. Water maintains body temperature through evaporation, as in sweating.
  3. Severe dehydration may result in cardiovascular problems.
  • Water toxicity (too much water) is also possible, resulting in dilution of important electrolytes (mineral salts) that may lead to irregular heart rhythm.
  • The estimated water requirement of an average adult is two liters per day.

Dietary fibre:

Dietary fibre (also known as “roughage”) is the part of the human food that is indigestible. It is found only in plant foods and it moves undigested through the stomach and small intestine and into the colon.


There are two types of dietary fibre:

  1. Insoluble dietary fibers:

Insoluble fibre travels through the small intestines quickly.


Wheat bran, whole grain breads and cereals, as well as the skins of many fruits and vegetables consist of insoluble fibres.

  1. Soluble dietary fibers:

Soluble fibre breaks down as it passes through the digestive tract, forming a gel. This gel traps some substances and it helps in lowering the blood levels of cholesterol and sugars.


Oats, beans, barley, and many fruits and vegetables are the sources of soluble fibres. Physicians recommended consuming 20 to 35 grams of fibre per day.


  1. Fibre prevents and relieves constipation by stimulating movement of the intestinal muscles.
  2. Increasing stool bulk and making stools softer and easier to pass.
  • It also controls weight by creating a feeling to fullness without adding too many calories to the diet.
  1. Dietary fibre can also reduce the risk of many other health conditions for example; avoiding constipation reduces the risk of developing haemorrhoids (swollen anal tissues).

Soluble fibre takes some acids away in the stool and in response, liver draws cholesterol from blood to make more acids, thus lowering blood cholesterol. Soluble fibre slow absorption of blood sugar from the small intestine, lowering blood sugar levels.

Insoluble fibre minimizes exposure to carcinogens (cancer causing agents) that may be in the stool by diluting them and speeding their movement through the bowel.

  1. Define balanced diet. How would you relate it with age, sex and activity?

Ans. Balanced diet:

Humans require various types of nutrients in order to keep them healthy and fit. These nutrients should be taken appropriately in diet. Diet is the food on which individual lives.

A balanced diet may be defined as the one which contains all the essential nutrients like carbohydrates, fats, proteins, minerals, vitamins in the correct proportion for the normal growth and development of the body. A balanced diet is related to the state of one’s age, sex and activity. It should not only take care of the different types of nutrients but also consider the energy requirements of the individual.

The following chart shows some of the common foods, taken in Pakistan, and the percentage of carbohydrates, lipids and proteins in each of them.

Foods Carbohydrates Lipids Protein
Bread (roti 52% 03% 09%
Rice 23% 0.1% 2.2%
Potato 19% 0.1% 02%
Apple 12.8% 0.5% 0.3%
Eggs 0.7 12% 13%
Milk 04% 04% 03%
Butter 0.4% 81% 0.6%
Chicken 0 11% 20%


Relation of balanced diet with age, gender and activity:

During growth period of the body there is higher metabolic rate in body cells and so the body needs a balanced diet that contains more energy. Adults needs less proteins per kg body weight, but a growing boy or girl needs more proteins per kg weight. Children need more calcium and iron for their growing bones and red blood cells respectively. Give below are the recommended daily requirements of energy. Gender has an impact on the requirements of a balanced diet. Women have comparatively les metabolic rate then the men of the same age and weight. Men need a balanced diet that provides comparatively more energy than the women require. Different people have different lifestyles and varied nature of work. A man with sedentary habits does not require as much energy as the man who is on his feet for most of the day.


Estimated energy requirements (in Kilocalories) according to age, gender and activity.




Age (years)

Activity level
Sedentary Moderately Active
Child male/female 2-3 1,000 1,000-1,400 1,000-1,400



4-8 1,200 1,400-1,600 1,400-1,800
9-13 1,600 1,600-2,000 1,800-2,000
14-18 1,800 2,000 2,400
19-30 2,000 2,000-2,200 2,400
31-50 1,800 2,000 2,200
50+ 1,600 1,800 2,000-2,200




4-8 1,400 1,400-1,600 1,600-2,2000
9-13 1,800 1,800-2,200 2,000-2,600
14-18 2,200 2,400-2,800 2,800-3,200
19-30 2,400 2,600-2,800 3,000
31-50 2,200 2,400-2,600 2,800-3,000
50+ 2,000 2,200-2,400 2,400-2,800


  1. Describe how protein energy, malnutrition, mineral deficiency disease and over intake of nutrients are the major forms of malnutrition?

Ans. Problems related to nutrition (malnutrition):

Problems related to nutrition are grouped as malnutrition.

Malnutrition is a term for the condition caused by an improper or insufficient diet. It most often refers to under nutrition resulting from inadequate consumption, poor absorption, or excessive loss of nutrients. Malnutrition also includes over nutrition, resulting from overheating or excessive intake of specific nutrients.

Most commonly, malnourished people either do not have enough calories in their diet, or are eating a diet hat lacks protein, vitamins, or trace minerals. Malnutrition weakness the immune system, impairs physical and mental health, slows thinking, stunts growth, hinders fetal development, and leads to infectious disease.

Major forms of malnutrition:

Common forms of malnutrition include:

  1. Protein energy malnutrition (PEM)

Protein-energy malnutrition refers to inadequate availability or absorption of energy and protein in the body. It is the leading cause of death in children in developing countries. Primary PEM results from a diet that lacks sufficient sources of protein and/or energy. Secondary PEM occurs as a complication of other diseases (AIDS, cancer, kidney failure, etc) that impair the body’s ability to absorb or use nutrients.

Diseases due to PEM:

PEM may lead to diseases such as Kwashiorkor and marasmus.


Is due to protein deficiency at the age of about 12 months when breastfeeding is discontinued, but it can also develop at any time during a child’s growing years. Children may grow to normal height but are abnormally thin.


Usually develops between the ages of six months and one year in children. Patients lost all their body fat and muscle strength, and acquire a skeletal appearance. Children with marasmus show poor growth and look small for their age.

  1. Mineral deficiency diseases:

Diseases resulting from the deficiency of a mineral are relatively rare among humans. Some examples are given below.


Goiter is a condition caused by an sufficient amount of iodine in the diet. Iodine is used by the thyroid gland to produce hormones that control the body’s normal functioning and growth. If sufficient iodine is not available in a person’s diet, the thyroid gland becomes enlarged and it results in swelling in the neck and the conditions is known as goiter.


Anemia is the most common of all mineral deficiency diseases. The term anemia literally means “a luck of blood”. The condition is caused when the number of red blood cells in reduced to a level lower than the normal. Haemoglobin molecule contains a single atom of iron at its center. If the body fails to receive sufficient amounts of iron, and adequate number of hemoglobin molecules will not be formed. In that case, there are not enough functioning red blood cells. A person becomes weak and listless.

  • Over-intake of nutrients:

Over-intake of nutrients (OIN) is a form of malnutrition in which more nutrients are taken than the amounts required for normal growth, development, and metabolism. The effects of over-intake of nutrients are usually intensified when there is reduction in daily physical activity (decline in energy expenditure).

The problems of over-intake of nutrients are increasing even in countries where hunger is common. There is a significant increase in the prevalence of overweight and obese individuals in developing countries. In Pakistan fast-food restaurants have changed the country’s eating pattern. Moreover, there is a greater tendency to snack between meals. Such behavior is more common among young people.

Over-intake of nutrients causes a number of health problems, for example, high intake of carbohydrates and fats leads to obesity, diabetes and cardiovascular problems. Similarly, high dose of a vitamin A causes loss of appetite and liver problems, and excess dose of vitamin D can lead to deposition of calcium in various tissues etc.

Effect of malnutrition:

An extended period of malnutrition can lead to problems like starvation, heart diseases, constipation and obesity.


Is a severe reduction in nutrient and energy intake and is the most horrible effect of malnutrition. In humans, prolonged starvation causes permanent organ damage and eventually results in death.

Heart diseases are also increasing on the global level and one of the causes who take unbalanced diet (high in fats) are more exposed to heart problems. Fatty foods increase blood cholesterol level, which obstructs the blood vessels leading to heart diseases. Often leads to situation where people cannot schedule their meals. This irregularity results in a number of health problems including constipation.


Means becoming over-weight and it may also be due to malnutrition. People who take food that contains energy more than their requirement and do very little physical work can become obese. Obesity is known as the mother-disease and may lead to heart problems, hypertension, diabetes etc.

  1. How would you advocate the unequal distribution of food, drought and flooding as the major causes of famine?

Ans. Famine, the major cause of malnutrition:


Famine is the lack of enough food to feed all the people living in area. It is a social and economic crisis that results in malnutrition and increased mortality. Historically, famines have occurred because of drought, crop failure, and because of man-causes such as war or misguided economic policies.

Major famines:

The most terrible famines of the twentieth century include the disaster in Bengal (1942-1945), famine in China (1928-1942), and famine in Ukraine (1932-33). The last great famines of this century were the disaster in Cambodia (1970s), the Ethiopian famine (1983-85) and the North Korean famine (1990s).


  1. Unequal distribution of food
  2. Drought
  • Flooding
  1. Increasing population
  2. Unequal distribution of food:

The achievements in science have enabled human beings to produce better food in terms of quality and quantity. Today the agricultural practices produce more than enough food that can be supplied to everyone on earth. But due to political and administrative problems the food is not equally distributed to the different regions of the world. The result is that there is always surplus food in countries like America, UK, and Canada etc and at the same time people have nothing to eat in countries like Ethiopia, Somalia etc.

  1. Drought:

A drought is a period of time when there is not enough water to support agricultural and human needs. A drought is usually due to an extended period to below-normal rainfall. Droughts decrease or even stop the crop yields resulting in famine.

iii. Flooding:

It occurs due to more than normal rainfall or due to weak water distribution system. River and canals overflow their blanks and destroy the soil quality of agricultural lands. It becomes impossible to grow crops immediately after flooding. In this way flooding may be a reason for short-term flooding in a country.

  1. Increasing population:

In spite of the global increase in food production, millions of human beings are undernourished. In the over-populated regions of the world large populations overuse natural resources to grow maximum food in order to meet the problems of food shortage. It leads to dry and infertile lands and depletion of resources. In such situations crops can no longer be grown and famines result.

  1. Define the process of digestion. Describe its different types?

Ans. Digestion:

There is a need of converting such large and non-diffusible molecules into smaller and diffusible molecules that can cross the membranes. This is achieved through the process of digestion.

Our cells require oxygen, water, salts, amino acids, simple sugars, fatty acids, and vitamins. These can cross cell membranes to enter the cells. Amino acids, simple sugars and fatty acids are rare in our environment. Such substances are usually parts of larger molecule like proteins, polysaccharides, and lipids, which cannot cross the membranes.

Mechanical digestion:

It involves mechanical digestion (mastication, the use of teeth to tear and crush food, and churning in the stomach).

Chemical digestion:

Chemical digestion (action of enzymes to break down complex molecules into simple structures).

Proteins are digested into their constituent amino acids, polysaccharides are digested into simple sugars (e.g. glucose), and lipids are digested into fatty acids and glycerol.

After digestion, the diffusible molecules are absorbed from the digestive system into the blood which carries them to body cells. In body cells the food molecules are assimilated (to get energy and to synthesize our own structures). At the same time the indigestible part of the food which remains in the digestive system is eliminated out of body through the process of defection. In simple words, our digestive system is responsible for the digested food, and the elimination of indigestible material.

  1. What is alimentary canal? Also describe the process of digestion in oral cavity?

Ans. Human alimentary canal:

The digestive system of human consists of a long tube that extends from the mouth to the anus. This tube is called alimentary canal and its main sections are oral cavity, pharynx, oesophagus, stomach, small intestines, and large intestine. In addition there are many glands associated with the alimentary canal. These are three pairs of salivary glands, the pancreas and the liver.

Oral cavity:

Oral cavity is the space behind mouth and has many important function in the whole process.

Food selection:

Food selection is one of them. When food enters the oral cavity, it is tested and felt. If the taste of mutton suggests that it is old, we reject it. If the teeth or tongue detect some hard object, such as dirt, we also reject that bite. The senses of smell and vision also help oral cavity in the selection of food.

Mechanical digestion:

The second function of oral cavity is the grinding of food by teeth. It is known as chewing or mastication. This is useful first because the oesophagus can pass only small pieces and secondly because enzymes cannot act on large pieced of food. They require small pieces with large surface areas to attack.

Partial digestion:

The third and fourth functions of the oral cavity are the lubrication and chemical digestion of food. The chewing process stimulates the three pairs of salivary glands (under the tongue, behind the jaws, and in front of ears) to release a juice called saliva in oral cavity.

Saliva has two main functions:

  1. First it adds water and mucous to the food which act as lubricant to ease the passage of food through oesophagus.
  2. Second, saliva contains an enzyme salivary amylase, which aids in the partial digestion of starch.

After the processes of chewing, lubrication and partial digestion the pieces of bread and mutton are rolled up by the tongue into small, slippery, spherical mass called bolus. We swallow the bolus and push it in oesophagus through the pharynx.

  1. Describe swallowing and peristalsis?

Ans. The bolus is swallowed then pushed down by the movement called peristalsis.


During swallowing the bolus is pushed to the back of the mouth by the tongue. The soft palate moves upward and the rear to close the opening of the nasal cavity. When swallowed, the bolus goes the pharynx, which makes special adaptions to prevent chocking or aspiration when food is swallowed. When larynx (the top of trachea) moves upward, it forces the epiglottis (a flap of cartilage) into more or less horizontal position thus closing the glottis i.e. opening of the wind pipe (trachea).

The beginning of the swallowing action is voluntary, but one the food reaches the back of the mouth, swallowing becomes automatic.

After being swallowed, the food enters the tube called the oesophagus, which connects the pharynx to the stomach. Neither the pharynx nor the oesophagus contributes to digestion and the previous digestive actions of saliva continue.


          Peristalsis moves the food from the oral cavity to the rectum. It is defined as the rhythmic sequence of waves of contraction in the smooth muscles of the walls of alimentary canal, thus squeezing the food down along the alimentary canal.

  1. Discuss the role of stomach in the process of digestion?

Ans. Stomach:

The stomach is dilated part of the alimentary canal.


It is J-shaped, located in the left of the abdomen, just beneath the diaphragm. Stomach has two main portions. The cardiac portion is present immediately after oesophagus and the pyloric portion is located beneath the cardiac portion.

Stomach has two sphincters (opening which are guarded by muscles). The cardiac sphincter is between stomach and oesophagus while the pyloric sphincter is between stomach and small intestine. The bolus enters the stomach from oesophagus through the cardiac sphincter.

Gastric juice:

When food enters stomach, the gastric glands found in the stomach wall are stimulated to secrete gastric juice.

Gastric juice of composed chiefly of:

  1. Mucous
  2. Hydrochloride acid
  • Pepsinogen (a protein-digesting enzyme)

Hydrochloric acid converts the inactive enzyme pepsinogen into its active form called pepsin. HCl also kills microorganisms present in food. Pepsin partially digest the protein portion of the food (bulk of mutton) into polypeptide and shorter peptide chains.

Churning in stomach:

In the stomach, food is further broken apart through a process of churning. The walls of the stomach contract and relax and these movements help in thorough mixing of the gastric juice and food. The churning action also produces heat which helps to melt the lipid content of the food.


When we bite off a piece of roti and mutton, chew it and then swallow it, there is some gastric juice already present in the stomach. Sometimes even the sight of food causes the releases of gastric juice.

Secretion of gastric juice:

When the bite is in oral cavity, message is conveyed to the brain in the form of nerve impulses. From the brain message is passed to the walls of the stomach for the secretion of some gastric juice. When food touches the walls of the stomach, more gastric juice is secreted. If we eat only a bite of bread, which has little protein in it, the stomach does not secrete more gastric juice.

On the other hand when we eat mutton, it results in the releases of abundant gastric juice. The reason is that when food reaches the stomach the already present gastric juice begins the digestion of any proteins present in it. The huge protein molecules are broken down into peptides.

These peptides stimulate some cells of the stomach walls to release a hormone called gastrin. This hormone enters blood and is distributed to a all parts of the body, including stomach. Here it has specific effect and stimulates the cells of gastric glands to secrete more gastric juice.

The starch in our bite of bread and the protein in mutton have been partially digested and the food has been converted to a soup-like mixture called chime. After it, the pyloric sphincter allows a little mass of chyme to enter duodenum.

  1. Discuss the role of small intestine during the process of digestion?

Ans. Small intestine:

Small intestine is comprises of three parts.

  1. Duodenum:

Duodenum comprises of the first 10 inches (25cm) of the small intestine and it is the part of the alimentary canal where most of the digestive process occurs. Here the food is further mixed with 3 different secretions.

  1. Bite from liver helps in fat digestion through emulsification.
  2. Pancreatic juice from pancreas contains enzymes trypsin, pancreatic amylase and lipase which digest proteins, carbohydrates and lipids respectively.
  • Intestinal juice from the intestine walls contains many enzymes for the complete digestion of all kinds of foods.
  1. Jejunum:

Next to the duodenum is 2.4 meters long jejunum. It is concerned with the rest of the digestion of the proteins, starch and lipids of our bite. Last 3.5 meters long part of the small intestine is the ileum. It is concerned with the absorption of digested food.

  • IIleum:

There are circular folds in the inner wall of the ileum. These folds have numerous finger-like projection called villi (singular: villus). The villi increase the surface area of the inner walls and it helps a lot in the absorption of digested food. Each villus is richly supplied with blood capillaries and a vessel of lymphatic system, called lacteal. The walls of the villus are only single-cell thick.

Transport of simple sugars and amino acids:

The digested molecules i.e. simple sugars and amino acids are absorbed from the intestine into the blood capillaries present in villi. The blood carries them away from the small intestine via the hepatic portal vein and goes to the liver for filtering, removal and toxins, and nutrient processing. Fatty acids and glycerol are absorbed into the lymphatic vessel (lacteal) present in villi, which carries them to the main lymphatic duct, from where they enter in bloodstream.

  1. What is the role of large intestine in the process of digestion?

Ans. Role of large intestine:

  1. Absorption of water:

After the digested products of our bite have been absorbed in blood, the remaining mass enters the large intestine. It has 3 parts, the caecum (or pouch that forms the T-junction with the small intestine), the colon, and the rectum. From colon water is absorbed into blood. As the water is absorbed, the solid remains of the food are called faeces. The faeces contain the undigested material. A large number of bacteria, sloughed off cells of the alimentary canal, bile pigments and water are also part of the faeces.

  1. Defecation:

Faeces are temporarily stored in the rectum, which opens out through anus. Under normal conditions when the rectum is filled up with faeces, it gives rise to a reflex and anus is opened for defecation. This reflex is consciously inhibited in adults but in infants it is controlled involuntarily. During growth, the child learns to bring this reflex under voluntary control.

  1. Write a comprehensive note on the role of liver?

Ans. Structure of liver:

A dark reddish organ, the liver is the largest gland of the body. In an adult human it weighs about 1.5kg and is the size of football. Liver lies beneath the diaphragm on the right side of the abdomen. It consists of a larger right lobe and a smaller left lobe. A pear-shaped greenish yellow sac, the gallbladder lies along the right lobe of liver on the ventral side.

Liver secrets bile, which is stored in the gallbladder. When the gallbladder contracts the bile is released into the duodenum through the common bile duct. Bile has bile salts which keep lipid droplets separate from one another, a process called emulsification. It helps the lipid-digesting enzymes to attack on lipids.

Role of liver:

Besides digestion, liver carriers out a number of other functions, some of which ae summarized here.

  1. Removes amino groups from amino acids (de-amination)
  2. Converts ammonia to a less toxic from the urea
  • Manufactures most of blood plasma proteins e.g. prothrombin and albumin
  1. Forms red blood cells in foetus.
  2. Destroys the old red blood cells.
  3. Manufactures blood clotting proteins called fibrinogen.
  • Synthesized non-essential amino acids.
  • Converts galactose and fructose to glucose.
  1. Converts glucose into glycogen and, when required, breaks glycogen into glucose.
  2. Converts carbohydrates and proteins into fats.
  3. Carries out the oxidation of fatty acids.
  • Forms lipoproteins, cholesterol and phospholipids.
  • Synthesized vitamin A from carotene, and activates vitamin D.
  • Produces heat to maintain body temperature.
  1. Stores fat-soluble vitamins (A, D, E and K) and mineral ions, such as iron.
  • Produces antiviral proteins e.g. interferon.
  1. Write a note on disorder of gut?

Ans. Disorders of gut:

Diarrhea, constipation and ulcer are the most common disorders of the gut that affect a number of people in Pakistan.



Diarrhea is a condition in which the sufferer has frequent watery, loose bowel movements. This condition may be accompanied by abdominal pain, nausea and vomiting. It occurs when required water is not absorbed in blood from the colon. If the colon is damaged or inflamed, absorption is inhibited, and watery stools results.


The main causes of diarrhea include lack of adequate safe water. Diarrhea is also caused by viral or bacterial infections.


          If sufficient food and water is available a patient recovers from diarrhea in a few days. However, for malnourished individuals diarrhea can lead to severe dehydration and can become life-threatening. The treatment for diarrhea involves consuming adequate amount of water to replace the loss, preferably mixed with electrolytes to provide essential salts and some amount of nutrients. Antibiotics may be required if diarrhea is due to bacterial infection.


Preventions of diarrhea include taking proper water and electrolytes, eating regularly and taking hygienic measures.


Constipation is a condition a person experience hard faeces that are difficult to eliminate. In severe cases it may lead to symptoms of bowel obstruction.


The main causes of constipation include hardening of the faeces due to excessive absorption of water through colon, insufficient intake of dietary fibre, dehydration, use of medicines (e.g. those containing iron, calcium, and aluminum), injured and sphincter and tumors in the rectum or anus.


Treatment of constipation is with a change in dietary and exercise habits. Enemas can be used to provide a form of mechanical stimulation. Laxatives (e.g. paraffin) may be necessary in some cases.


Constipation is usually easier to prevent than to treat. One should take the required quantities of water and dietary fibres.



Ulcer (peptic ulcer) is a sore in the gut lining caused by a gradual breakdown of the tissue by the acidic gastric juice. Ulcer of the stomach is called a gastric ulcer; of the duodenum, a duodenal ulcer; and of the oesophagus, an oesophagus ulcer.


The signs and symptoms of ulcer include abdominal burning after meals or at midnight. Severe ulcers may cause abdominal pain, rush of saliva after and episode of regurgitation, nausea, loss of appetite and weight loss. Ulcer is treated with medicines containing alkaline composition.


The causes of ulcer include excess acid, infection, long term use of anti-inflammatory medicines (including aspirin), smoking, drinking, coffee, colas, and eating spicy foods.


Preventive measures should be adopted for such complication. Spicy foods and those containing more acidity should be avoided. As smoking is a major factor of ulcer, it should be avoided.

Ch#  9        TRANSPORT

Q.1. Tick the correct answer.                                 
1. In most plants the food is transported in the form of?
(a) Glucose (b) Sucrose (c) Starch (d) Proteins
2. Stomata close when the guard cells?
(a) Lost water become turgid (b) Gain chloride ions (c) Become turgid (d) Gain potassium ions
3. When fibrinogen makes blood clot it separates from blood and the remainder is called?
(a) Plasma (b) Lymph (c) Serum (d) Pus
4. What is correct about human red blood cells?
(a) Have limited life span (b) Are capable of phagocytosis (c) Produce antibodies (d) Are multinucleate
5. Which of the following tissue layer is found in all blood vessels?
(a) Smooth muscle (b) Endothelium (c) Skeletal muscle (d) Connective tissue
6. When do the atria contract?
(a) Before disable (b) After systole (c) During diastole (d) During systole
7. Which of the following contains deoxygenated blood in an adult human?
(a) Left atrium (b) Pulmonary artery (c) Pulmonary vein (d) All of the above
8. Which of the following chambers has the thickest walls in human heart?
(a) Right atrium (b) Left atrium (c) Left ventricle (d) Right ventricle
9. Which of these statements is correct about the circulatory system?
(a) It transports hormones (b) Capillaries have thicker walls then veins (c) Systematic circulation carries blood to and from the lungs (d) All of the above are true



Q2. Answers the following short questions.

  1. What are lenticels and where are they found in plant body?

Ans. Lenticels are five openings present in the stems of some plants. They are produced during secondary growth of the plant.

  1. What is the role of potassium ions in the opening of stomata?

Ans. Light causes the movement of potassium ions from epidermal cells into guard cells. Water follows these ions and enter the guard cells. Thus their turgidity increases and stoma opens.

  1. Define the cohesion-tension theory?

Ans. Cohesion-tension body states that, the force which carries water (and dissolved materials) upward through xylem is transpiration pull. Transpiration creates a pressure difference that pulls water and salts up from roots.

  1. What do you mean by sources and sinks according to the pressure flow mechanism?

Ans. According to pressure flow mechanism, sources include the exporting organs, typically a mature leaf or storage organs, while sinks are the areas of active metabolism or storage and growing regions.

  1. What are the two main types of white blood cells? How do they differ?

Ans. There are two main types of white blood cells.

  1. Granulocytes: they have granular cytoplasm.
  2. Agranulocytes: they have clear cytoplasm.
  3. You see pus at the site of infection on your skin. How is it formed?

Ans. White blood cell die in the process of killing the germs. These deal cells accumulate and make the white substance called pus, seen at the site of infection sites.

  1. What role does the pericardial fluid play?

Ans. Pericardial fluid reduces friction between pericardium and heart, during heart contractions.

  1. Define the terms systole and diastole?

Ans. Contraction of heart muscles is called systole and relaxation of heart muscles is called diastole.

Q3. Answers the following long questions

  1. Which substances are transported through plants? Also name plant tissues involved in transport of these substances?

Ans. Transport in plants:

Water is vital to plant life. It is necessary not just for photosynthesis and turgor, but much of the cellular activities occur in the presence of water molecules and the internal temperature of the plant is also regulated by water. Land plants get water and minerals form soil.

After absorption by the roots, these water and minerals have to be transported to the aerials parts of the body.

Similarly during photosynthesis food is manufactured in leaves. This food is transported to the other parts of the body for utilization and storage.

All land plants (except of mosses and liverworts), have developed complex vascular systems that move water and food throughout the plant body. These vascular tissues are called xylem and phloem.

  1. How would you related the internal structure of root with the uptake of water and salts?

Ans. In addition to anchoring the plant, roots perform two vital functions.

  1. They absorb water and salts from the soil.
  2. They provide conducting tissues for disturbing these substances to the tissues of the stem.

Conducting tissues:

The conducting tissues (xylem and phloem) of the root are grouped in the center to form a rod-shaped core, which extends throughout the length of the root.


          Outside the conducting tissues, there is a narrow layer of thin-walled cells, the Pericycle.


A single layer of cells, the endodermis, surrounds the Pericycle layer.


The remaining tissues of the root consist of a board zone of large, thin-walled cells making up the cortex.


The cortex is bounded on the outside by a single layer of epidermal cells.

Root hairs:

Roots also have clusters of tiny root hairs, which are actually the extensions of epidermal cells.

Absorption of water and salts:

Root hairs provide large surface area of absorption. They grow out into the spaces between soil particulars where they are in direct contact will the water. They cytoplasm of the root hairs has higher concentration of salts than the soil water, so water moves by osmosis into the root hairs, water and salts must move through the epidermis and cortex of the root, and then into the xylem tissue in the center of the root.

There are two pathways through which water travels from the outside of the root to the inside.

Apoplast pathway:

In the Apoplast pathway, water travels along cell walls and through intercellular spaces to reach the core of the root.

Symplast pathway:

In the Symplast pathway, water moves across the root hair membrane and through the cells themselves, via channels (Plasmodesmata) that connect their contents.

Once in the xylem, the water can be carried to all the aerial part of the plant.

  1. Define transpiration and relate it with cell surface and with stomatal opening and closing?

Ans. Transpiration:

Transpiration is the loss of water from plant surface through evaporation. This loss may occur:

  1. Through stomata in leaves.
  2. Through the cuticle present on leaf epidermis.
  • Through special openings called lenticels present in the stems of some plants.

Water is drawn from the xylem into mesophyll cell, from where it comes out and makes a water-film on the cell walls of the mesophyll. From here water evaporates into the air spaces of the leaf. By diffusion, water vapors then move from the air spaces towards the stomata and then pass to the outside air.

Opening and closing of stomata:

Most plants keep their stomata open during the day and close them at night. It is the responsibility of the stomata to regulate transpiration via the actions of the guard cells.

Structure of stomata:

The two guard cells of a stoma are attached to each other at their ends. The inner concave sides of guard cells that encloses a stoma are thicker than the outer convex sides.

Opening of stomata:

When these guard cells get water and become turgid, their shapes are like two beans and the stoma between the opens.

Closing of stomata:

When the guard cells loose water and become flaccid, their inner sides touch each other and the stoma closes.

Mechanism of opening and closing of stomata:

The concentration of solutes (glucose) in the guard cells is responsible for the opening and closing of stomata. Recent studies have revealed that stomata actually open and close due to the movement of potassium ions in and out of guard cells. According to these studies, blue wavelengths of daylight open stomata by allowing ‘K’ to flow into the guard cells, from the surrounding epidermal cells. Water passively follows these ions into the guard cells, and as their turgidity increases the stoma opens.

As the day progresses, guard cells make glucose. Due to higher concentration glucose, their water potential decreases and water stays in them. At the end of the day the ‘K’ flow back from guard cells to the epidermal cells and the concentration of glucose also falls. This initiates the loss of water and reduced turgor pressure in guard cells, which causes the closure of stoma.

  1. How do different factors affect the rate of transpiration?

Ans. Factors affecting the rate of transpiration:

  1. Light:

The rate of transpiration is directly controlled by the opening and closing of stomata and it is under the influence of light. In strong light the rate of transpiration is very high as compared to dim light or no light.

  1. Temperature:

Higher temperature reduces the humidity of the surrounding and also increases the kinetic energy of water molecules. In this way it increases the rate of transpiration. The rate of transpiration doubles with every rise of 10  in temperature but very high temperature i.e. 40-45  causes closure of stomata, so that transpiration stops and plant does not loses the much needed water.

  • Moisture:

When air is dry, water vapors diffuse quickly from the surface of mesophyll cells into leaf air spaces and then from air spaces to outside. This increases the rate of transpiration. In humid air the rate of the diffusion of water vapors is reduced and the rate of transpiration is low.

  1. Wind:

Wind (air in motion) carries the evaporated water from leaves and it causes an increase in the rate of evaporation from the surfaces of mesophyll. When air is still, the rate of transpiration is reduced.

  1. Surface area of leaf:

The rate of transpiration also depends upon the surface area of leaf. More surface area provides more stomata and there is more transpiration.

Significance of transpiration:

Transpiration is called a necessary evil. It means that transpiration is a potentially harmful process but is unavoidable too. Transpiration may be a harmful process in the sense that it requires wet surfaces from which evaporation can occur and during the conditions of drought loss of water from the plant results in wilting, serious desiccation and often death of the plant. This is the reason that at high temperatures, plant close their stomata and reduce transpiration rate to prevent wilting.

On that other hand, transpiration in necessary too.

  1. It creates a pulling force called transpirational pull which is principally responsible for the conduction of water and salts from roots to the aerial parts of the plant body.
  2. When water transpires from the surfaces of the plant, it leaves a cooling effect on plant. This is especially important in warmer environmental. Moreover, the wet surfaces of leave cells allow gaseous exchange.
  3. Explain the movement of water in terms of transpirational pull?

Ans. Transportation of water:

The issue of the processes by which water is raised through columns of considerable height at times has been studied and debated for years in botany circles. The end result is the cohesion-tension theory.

According to this theory the mechanism by which water (along with dissolved materials) is carried upward through the xylem is transpirational pull. Transpiration creates a pressure difference that pulls water and salts up from the roots.

When a leaf transpires (loses water), the water potential of its mesophyll cells drops. This drop causes water to move by osmosis from the xylem cells of leaf into the mesophyll cells. When one water molecules moves up by the xylem of the leaf, it creates a pulling force that continues all the way to the root. This pulling force created by the transpiration of water is called transpirational pull. It also causes water to move transversely (from root epidermis to cortex and Pericycle).

Following are the reasons for the creation of transpirational pull.

  1. Water is held in a table (xylem) that has small diameter.
  2. Water molecules adhere to the walls of xylem tube (adhesion).
  • Water molecules cohere to each other (cohesion) and do not contain dissolved gases (which would otherwise come out of water and form bubbles).

These attractions allow an overall tension among water molecules and form ‘columns’ of water. The columns of water move from root to shoot and the water content of the soil supplies water to the ‘columns’.

  1. Describe the theory of pressure flow mechanism to explain the transaction of food in plants.

Ans. Translocation of food:

Phloem is responsible for transporting food substance throughout the plant. The glucose formed during photosynthesis in mesophyll cells, is used in respiration and the excess of it is converted into sucrose. In most plants the food is transported in the form of sucrose.

Pressure flow theory:

As with water movement in plants, the movement of food in plants has been studied and debated for years. The currently accepted hypothesis states that the transport of food is through pressure-flow mechanism. In pressure-flow mechanism the food from sources to sink.


The sources include any exporting organs typically a mature leaf or storage organ.


Sinks are the areas of active metabolism or storage, for example roots, tubers, developing fruits and leaves, and the growing regions. A storage organ is capable of storing food and exporting the stored materials.

For example root of beet is a sink in first growing season, but becomes source in the next growing season, when sugars are utilized in the growth of new shoots.


At the source, the food (sugars) is moved by active transport into the sieve tubes of the smallest veins. Due to the presence of sugar in sieve tubers, their solute concentration increases and water enters them from xylem via osmosis. This results in higher pressure in these tubes, which drives the solution towards the sink.

Unloading of sieve tubes:

          At the sink end, the food is unloaded by active transport. Water also exists from the sieve tubes. The exit of water decreases the pressure in sieve tubes, which causes a mass flow from the higher pressure at the source to the now lowered pressure at the sink. In other words, the mass flow is caused by drops in pressure at the sink as the food and water molecules are removed.

  1. Define open and closed circulatory system?

Ans. Closed circulatory system:

Like other vertebrates, humans have a closed blood circulatory system (meaning that the blood never leaves the network of arteries, veins and capillaries).

The main components of the human blood circulatory system are the blood, the heart, and the blood vessels.

Open circulatory system:

Some invertebrates like arthropods have open circulatory system. In their bodies blood does not remained confined in the blood vessels and bathes all the body organs in blood of white color (haemolymph).

  1. List the functions of the components of blood.

Ans. Blood:

Blood is a specialized bodily fluid (considered a specialized form of connective tissue) that is composed of a liquid called blood plasma and blood cells suspended within the plasma.

The weight of blood in our body is about 1/12th of our body. The average adult has a blood volume of roughly 5 liters. In a healthy person, plasma constitutes about 55% by volume of the blood, and cell or cells-like bodies about 45% by volume of the blood.

Blood plasma:

Plasma is primarily water in which proteins, salt, ions, metabolites and wastes are dissolved. Water constitutes about 90-92% of plasma, 8-10% are dissolved substances. The materials present in the water of plasma can be divided into following six categories.

  1. The salts make up 0.9% of the plasma, by weight. More than two thirds of this amount is sodium chloride (the table salt). Salts of bicarbonate are also present in considerable amounts. Ca, Mg, K and Zn are found in trace amounts. Changes in the concentration of particular ion can create serious disturbances e.g. change in the pH of blood. The normal pH of human blood is 7.4 and it is maintained in narrow limits. Any change in blood pH affects the reactions of the body.
  2. Proteins constitute 7-9% by weight of the plasma. Antibodies are produced by lymphocytes (a type of white blood cells), in response to antigens and then passed to plasma and lymph. They are a part of body’s immune system. Fibrinogen is a plasma protein that takes part in the blood clotting process. The protein prothrombin acts as catalyst in blood clotting process. The protein circulate in the blood and maintain the water balance of blood. They do not let water go out of blood.
  • Organic nutrients in blood include glucose, lipids, and amino acids etc. They enter the blood after being absorbed from the digestive system.
  1. Plasma also contains nitrogenous waste products formed as a result of cellular metabolism. In cells they are produced in the form of ammonia. Plasma carries ammonia to liver where it is converted into different (less toxic) forms, which are then carried to kidneys for removal.
  2. Hormones, which work as an important part of body’s coordination system, are carried by blood plasma.
  3. Respiratory gases and  are present in the plasma of the blood  is primarily carried by RBCs but small amount of it are also carried as dissolved in plasma. Most of the  is carried by plasma.

Blood cells (and cell-like bodies):

Blood contains different types of cell that are exceptional from other cells of body in having the feature of being circulated throughout the body.

These cells are of three types:

  1. Red blood cells (erythrocytes):


These are the most numerous of blood cells. A cubic millimeter of blood contains 5 to 5.5 million of them in males, and 4 to 4.5 million in females.


These cells, when formed, have nucleus. In the RBCs of mammals the nucleus, mitochondria, endoplasmic reticulum etc. are lost when they get mature and before they enter blood.


About 95% of the cytoplasm of red blood cells in filled with hemoglobin, which transports  and small amount of . The remaining 5% consists of enzymes, salts and other proteins. These cells once mature, do not divide. RBCs are biconcave and have an elastic cell membrane. The average diameter of erythrocytes is 08 m. In the embryonic and foetal life, they are formed in liver and spleen. In adults, they are formed principally in the red bone marrow of short and flat bones, such as the sternum, ribs and vertebrate.

Life span:

The average life span of a red blood cell is about four months (120 days) after which it breaks down in liver and spleen by phagocytosis.

  1. White blood cells (leukocytes):

These blood cells are colorless, as they do not contain pigments. They are not confined to blood stream, as they also migrate out into the tissue fluid.


There are 1 or 2 leukocytes for every 1000 RBCs. One cubic millimeter of blood contains 7000 to 8000 of them.


They are much larger (two three times) that the blood cells.

Life span:

They have life span of months or even years, but this depends on body’s needs.


There are 5 types of leukocytes which can be divided into 2 main types.

  1. Granulocytes:

Are the leukocytes with granular cytoplasm. These include neutrophils, eosionophils and basophils. They are formed in the red bone marrow.


Their nucleus is divided into 2-5 lobes. They destroy small particles by phagocytosis. They are the 62% of the leukocytes and their average life span is 07 hours.


Their nucleus is bilobed and they provide defense against parasites. They are 2% of the leukocytes and their life span depends upon needs.


Their nucleus is bilobed and they prevent blood clotting by releasing an anticoagulant, heparin. They are also responsible for developing inflammatory responses, when they rupture and release the inflammatory agent, the histamines. They are less than 1% of leukocytes and their life span depends upon needs.

  1. Agranulocytes:

Are the leukocytes with clear cytoplasm. These include monocytes and lymphocytes (B&T lymphocytes). They are formed in the lymphoid tissue of lymphatic system i.e. in lymph nodes, spleen, tonsils, adenoids and thymus.


Their nucleus may be rounded or lobed. They are 3% of leukocytes with life span of 3 days. After entry into the inflamed tissues, they become macrophages and engulf the germs and the dead cells.


They have large nucleus which fills almost all of the cytoplasm. They are 32% of leukocytes and are the major component of the immune system.

Lymphocytes include:

  1. B lymphocytes:

They recognize antigens and synthesize antibodies against them.

  1. T lymphocytes:

They recognize antigens and then combat them in different ways.

Platelets (thrombocytes):

They are not cells, but are fragments of large cells of bone marrow, called megakaryocytes.


They do not have any nucleus and any pigment.


One cubic millimeter of blood contains 250,000 platelets.

Life span:

The average life span of a blood platelet is about 7 to 8 days.


Platelets help in conversion of fibrinogen, a soluble plasma protein, into insoluble form, fibrin. The fibrin threads entangle with the red blood cells and other platelets in the area of damaged tissue, ultimately forming in blood clot. When fibrinogen is transformed into fibrin and its fibres separate, the underlying matter is called serum. The clot serves as a temporary seal to prevent bleeding until the damaged tissue is repaired.

  1. Write a note on the functions of blood?

Ans. Functions of blood:

The overall functions of human blood can be summarized as follows:


Blood is the major agent for the transport of materials in the body including blood from the endocrine tissues to the target sites.


Blood helps in body’s defense against diseases. Blood has particular proteins e.g. interferon (produced by liver) and nucleic acids and toxins of invading organisms.


Blood acts as a buffer to maintain the acid-base balance i.e. concentration of hydrogen and hydroxyl ions in the body.

Blood help ion maintaining body’s temperature and concentration of water and salts. Blood is also responsible for maintaining the amounts of chemicals in the body to constant or nearly constant levels. It thus helps in homeostasis.

Blood helps in the exchange of materials between blood and body tissue through blood capillaries. Blood helps in the exchange of materials between blood and body tissue through blood capillaries.

  1. State the signs and symptoms, causes and treatments of leukemia and thalassemia?

Ans. Blood disorders:

There are many types of blood disorders, including bleeding disorders, leukaemia, thalassemia etc. here we would discuss leukaemia and thalassemia.

Leukaemia (blood cancer):

Cancer means the uncontrolled production of cells. Leukaemia is characterized by the appearance of great number of immature and abnormal white blood cells in the bone marrow and often in the spleen and liver.

Cell types Description Average number present Major functions
Red blood cells (erythrocytes) Like a biconcave disc; contain haemoglobin, 8um in dm 5,000,000 per Transport oxygen and a small amount of
White blood cells (leukocytes) 7500 per Body’s defense
Granulocytes i.                 Neutrophils About twice the size of RBCes nucleus 3-5 lobed 62% of WBCes Destroy small particles by phagocytosis
ii.                Eosinophils About twice the size of RBCes nucleus bilobed 2% of WBCes Inactivates inflammatory substances attacks parasites
iii.              Basophils About twice the size of RBCes nucleus bilobed Less than 1% of WBCes Releases anticoagulant (heparin) and histamine which causes inflammation
Agranulocytes i.                 Monocytes 3-4 times larger than RBCes nucleus round or blood 3% of WBCes Give rise to macrophages which destroy particles by phagocytosis
ii.                Lymphocytes Slightly larger than RBCes nucleus nearly fills cell 32% of WBCes Produce antibodies
Platelets Fragments of bone marrow cells (megakaryocytes) 250,000 per Involving in blood clotting
Plasma Description Amount in %age Major functions
Liquid portion of blood 55% by volume Carries blood cells and important blood proteins, hormones, salts, etc



This is caused by a cancerous mutation in bone marrow cells or in the lymph tissues cells and results in uncontrolled production of white blood cells (leukocytes).


The mutated bone marrow cells may spread throughout the body, so that white blood cells are produced in many other organs. These white blood cells are not completely differentiated and so are defective. This disease may be of different kinds depending on the type of white blood cells, nuetrophilic leukaemia. Eosinophilic leukaemia, basophilic leukaemia, monocytic leukaemia or lymphocytic leukaemia.


It is a very serious disorder and the patient needs to change the blood regularly with the normal blood, got from donors. It can be cured by bone marrow transplant which is in most cases effective, but very expensive treatment.

Thalassemia (g. thalassemia= sea; haem= blood):

It is also called a Cooley’s anaemia on the name of Thomas B. Cooley it is also called a Cooley’s anaemia on the name of Thomas B. Cooley, an American paediatrican (the physician who treats children).


It is a genetic problem due to mutations in the gene of haemoglobin.


Haemoglobin molecule in most cases of thalassemia, does not have- chains in it, instead F-chain is present (F: foetal haemoglobin). This is called- thalassemia and the patient cannot transport oxygen properly.


The blood of these patients is to be replaced regularly, with normal blood. It can be cured by bone marrow transplant which is very expensive and does not give 100% cure rate.

The world celebrates the international thalassemia day on 8th of May. This day is dedicate to raise public awareness for prevention of thalassemia and to highlight the importance of the care for thalassemia in all countries.

  1. How do we classify blood groups in terms of the ABO and the Rh blood group systems?

Ans. Blood group system:

Blood group system are a classification of blood on the presence or absence of antigens on the surface of red blood cells. An antigen is a molecule that can stimulate an immune response (antibody production etc). These antigens may be proteins or polysaccharides, depending on the blood group system.

ABO blood group system:

It is the most important blood group system in humans. It was discovered by the Austrian scientists Karl Landsteiner, who found four different blood groups (blood types) in 1900. He was awarded the Nobel Prize in Medicine for his work.

Blood groups:

In this systems, there are four different blood groups which are distinct from each other on the basis of specific antigens (antigen A and B) present on the surface of RBCs.

  1. A person having antigen A has blood group A.
  2. A person having antigen B has blood group B.
  • A person having both antigens has blood group AB.
  1. A person having none of the A and B antigens has blood group O.

After birth, two types of antibodies i.e. anti- A & anti-B antibodies appear in the blood of individuals. These antibodies are present according to the absence of corresponding antigen. In persons with blood group A, antigen A is present and antigen B is absent. So their blood serum will contain anti-B antibodies. In persons with blood group AB, antigens A & B present i.e. neither is absent. So their blood serum will contain no antibody. In persons with blood group O, neither antigen A nor antigen B is present i.e. both are absent. So their blood serum will contain both, antigen A & anti B, antibodies.

Blood transfusion in ABO blood group system:

Blood transfusion in the process of transferring blood or blood-based products from one person into the circulatory system of another. Blood transfusions can be life-saving in some situations, such as massive blood loss due to injury, or can be used to replace blood lost during surgery. People suffering from anaemia, haemophilia, thalassemia or sickle-cell disease may require frequent blood transfusions.

Transfusions of blood is done after confirming that no agglutination results in the blood of recipient. Agglutination leads to the clumping of cells and clumped cells cannot pass through capillaries. For the confirmation of no agglutination, blood samples of donor and recipient are crossed-matched for compatibility. Antibodies of the recipient’s blood may destroy the corresponding antigen-containing RBCs of the donor or the antibodies of the donor’s blood may destroy the antigen-containing RBCs of the recipient.

O blood group individuals are called universal donors, because they can donate blood to the recipients of every other blood group. AB blood group individuals are called universal recipients, because they can receive transfusion from the donors of every other blood group.

  1. What four chambers make the human heart and how blood flows through these chambers?

Ans. Human heart:

The heart is usually felt to be on the left side because the left chamber of the heart i.e. (left ventricle) is stronger (it pumps blood to all body parts).

The heart is a muscular organ responsible for pumping blood through the blood vessels by repeated contractions.

The term cardiac means “related to the heart”. The bulk of the walls of the heart chambers is made of cardiac muscles.

Structure of heart:

In the human body, the heart is situated between the lungs, in the middle of the chest cavity (thorax) underneath the breathstone.

The heart is enclosed in a sac known as the pericardium. There is a fluid, known as pericardial fluid, between the pericardium and the heart walls. It reduces friction between the pericardium and the heart, during heart contractions.

The human consists of four chambers. The upper thin-walled chambers are called the left and right atria (singular ‘atrium), and the lower thick-walled chambers are called the left and right ventricles. The left ventricles is the largest and strongest chamber in heart.

Human heart works as a double pump i.e. It receives deoxygenated (with less oxygen blood from body and pumps it to the lungs and, at the same time, it receives oxygenated (with more oxygen) blood from lungs and pumps it to all the body.

Inside heart chambers the deoxygenated and oxygenated bloods are kept separated. Here is a brief description of the circulation of blood inside heart to shoe its double-pump mechanism.

The right atrium receives deoxygenated blood from the body via the main veins i.e. superior and inferior vena cavae.

When right atrium contracts it passes the deoxygenated blood to get the right ventricle.

The opening between the right atrium and the right ventricle is guarded by a valve known as tricuspid valve (because it has 3 flaps).

When right ventricle contracts, the blood is passed to pulmonary trunk, which carries blood to the lungs. The tricuspid valve prevents the back flow of blood from right ventricle to the right atrium.

At the bases of the pulmonary trunk, pulmonary semilunar valve is present which prevents trunk to the right ventricle.

The walls of left ventricle are the thickest one. These are about a half-inch thick. They have enough force to push blood into the body. This gives an evidence that the structure of the parts of heart are adaptive to their functions.

The oxygenated blood from the lungs is brought by pulmonary veins to left atrium. The left atrium contracts and pumps this blood to the left ventricle. The opening between the left atrium and the left ventricle is guarded by a valve known as bicuspid valve (because it has two flaps).

When the left ventricle contracts, it pumps the oxygenated blood in aorta, which carries the blood to all parts of the body (except lungs).

The bicuspid valve prevents the backflow of blood from the left ventricle to the left atrium. At the base of aorta the aortic semilunar valve is present which prevents the backflow of blood from aorta to the left ventricle.

Both atria are filled simultaneously. They contract together to pump the blood to both the ventricles. Similarly, both ventricles. Similarly, both ventricles contract simultaneously to pump the blood out of heart.

Right side of the heart collect the deoxygenated blood from body and distributes it to the lungs while the left side collect the oxygenated blood from lungs and distributes it to the body. The pathway on which deoxygenated blood is carried from the heart to the lungs and in return oxygenated blood is carried from the lungs to the heart is called pulmonary circulation or circuit.

The pathway on which oxygenated blood is carried from the heart to the body tissues and in return deoxygenated blood is carried from the body tissues to the heart is called systemic circulation or circuit.

The blood in pulmonary circulation is at lower pressure than the blood in the systemic circulation. It gives sufficient time for gaseous exchange to occur in the lungs.

  1. Write a short note on cardiac cycle?

Ans. Cardiac cycle:

The relaxation of heart chambers fills them with blood and contraction of chambers propels the blood out of them. The alternating relaxations and contractions make up the cardiac cycle and one complete cardiac cycle makes one heartbeat. The complete cardiac cycle consist of following steps:

Cardiac diastole:

The atria and ventricles relax and blood is filled in atria. This period is called cardiac diastole.

Atrial systole:

Immediately after their filling, both atria, contract and pump the blood towards ventricles. This period in cardiac cycle is called atrial systole.

Ventricular systole:

When both ventricles contract and pump, the blood towards body and lungs. The period of ventricular contraction is called ventricular systole.

In one heartbeat, diastole lasts about 0.4 sec, atrial systole takes about 0.1 sec, and the ventricular systole lasts about 0.3 sec.

  1. Write a note on heart rate and pulse rate?

Ans. Heart rate and pulses rate:

The heart rate is the number of times the heart beats per minute. A resting heart rate anywhere between 60 and 90 (70 is average) is considered in the normal range.

The heart rate sufficient a lot depending on factors such as activity level and stress level.

The heart rate can be measured by feeling the pulse. Pulse is the rhythmic expansion and contraction of an artery as blood is forced through it by the regular contractions o the heart.

  1. Compare the structure and function of an artery, a vein and a capillary?

Ans. Blood vessels:

The third part of the blood circulatory system are the blood vessels, which function to transport blood throughout the body. The most important vessels in the system are the arteries, veins, and capillaries.


Arteries are the blood vessels that carry blood away from the heart. In adults, all arteries with the exception of the pulmonary arteries, carry oxygenated blood.

Their structure shows that arteries are well adapted to their function. The walls of an artery are composed of three layers. The outermost layer is known as the tunica externa and it is composed of connective tissue.

          The middle layer is the tunica media and is made up of smooth muscles and elastic tissue. The innermost layer is the tunica intima and is made up of mainly endothelial cells. The hollow internal cavity in which the blood flows is called the lumen.


Capillaries are the smallest blood vessels, which are formed by the divisions of arterioles. The exchange of materials between blood and tissue fluid is carried out through the capillaries.

The walls of capillaries are composed of only a single layer of cells, the endothelium. This layer is so thin that molecules such as oxygen, water and lipids can pass through them and enter the tissue fluid. Waste products such as carbon dioxide and urea can diffuse from tissue fluid into the blood.

  1. Write a note plan of human blood circulatory system?

Ans. General Plan of human blood circulation system:

Many scientists worked for discovering the facts about the circulation of blood in human body. Two important scientists who revealed much knowledge of the blood circulatory system were Ibn-e-Nafees and William Harvey. Ibn-e-Nafees (1210-1286) was a physician and he is honored as the first scientists who described the pathway of blood circulation. William Harvey (1578-1657) discovered the pumping action of heart and the pathway of blood in major arteries and veins.

Now we will see how the major arteries and veins make the arterial an venous systems respectively.

The arterial system:

The large pulmonary trunk emerges from the right ventricle and divides into right and left pulmonary arteries, which carry the deoxygenated blood to the right and the left lungs.

The oxygenated blood leaving the left ventricle of the heart is carried in a large artery, the aorta. The aorta ascends and forms an aortic arch. The arch curves left and descends inferiorly into the body. Form the upper surface of the aortic arch three arteries emerge, which supply blood to head, shoulders and arms. As the aorta passes down through the thorax, it becomes the dorsal aorta. The dorsal aorta gives off many branches and the important ones are listed here.

Several intercostal arteries supply blood to the digestive tract while the hepatic artery supplies blood to the liver. Inferior to these are a pair of renal arteries that supply the kidneys. The gonadal arteries serve the gonads. Just below the gonadal arteries is the inferior mesenteric artery, which serves a part of the large intestine and rectum. Then the aorta divides into two common iliac arteries, each of which divides into an internal iliac artery, and an external iliac artery. Each external iliac becomes the femoral artery in the upper thigh. It gives branches of thigh, knee, shank, ankle and foot.

Even though the heart chambers are continually bathes with blood, this does not nourish the heart muscles. The blood supply to the heart muscles is provided by the coronary arteries, which emerge from the base of the aorta. The heart muscles are drained by the coronary veins, which empty into right atrium. The coronary arteries and veins are collectively called coronary circulation and it is a part of the systemic circulation.

The veins from lungs, called pulmonary veins return the oxygenated blood to the left atrium of the heart.

Two major veins i.e. the superior vena cava and the inferior vena cava, carrying the deoxygenated blood from the rest of the body, empty into the right atrium.

The superior vena cava forms when different veins from the head, shoulders and arms join together. Form the legs, the oxygenated blood is returned to the heart by many veins which empty into the inferior vena cava. Veins carrying blood from calf, foot and knee, join together to form the femoral vein. It empties into the external iliac vein which joins with the internal iliac and both empty into the common iliac vein. The right and left common iliac veins join to form the inferior vena cava, among these are the hepatic, renal veins, and the gonadal veins.

All the veins coming from the stomach, spleen, pancreas, and intestine drain into the hepatic portal vein, which carries the blood the liver. Form liver, a hepatic veins carries blood and empties into the inferior vena cava. The two renal veins carry blood from the kidneys while the two gonadal veins carry blood from gonads to the inferior vena cava. In the thoracic cavity the inferior vena cava also receives veins from thoracic walls.

  1. Define cardiovascular disorders?

Ans. Cardiovascular disorders:

The diseases that involve the heart of blood vessels (arteries and veins) are collectively called cardiovascular disorders. These diseases have similar causes, mechanisms, and treatments.

The risk factors that lead to cardiovascular disorders include advanced age, diabetes, high blood concentration of low-density lipids (e.g. cholesterol) and triglycerides, tobacco smoking, high blood pressure (hypertension), obesity, and sedentary lifestyle.

There is therefore increased emphasis on preventing cardiovascular disorders by modifying risk factors, such as healthy eating, exercise and avoidance of smoking.

  1. How would you differentiate between atherosclerosis and arteriosclerosis?

Ans. Atherosclerosis:

Atherosclerosis is a disease affecting arteries. It is commonly referred to as a “narrowing” of the arteries.


It is a chronic diseases in which there is accumulation of fatty materials, abnormal amounts of smooth muscles, cholesterol, or fibrin in the arteries.


When this condition is severe, the arteries can no longer expand and contract properly, and the blood move through them with difficulty.


The accumulation of cholesterol is the prime contributor to atherosclerosis. It results in the formation of the multiple deposits called plaques within the arteries. Plaques can form blood clots called thrombus within arteries. If a thrombus dislodges and becomes free-floating, it is called an embolus.


Arteriosclerosis is a general term describing any hardening of arteries. It occurs when calcium is deposited in the walls of arteries. It can happen when atherosclerosis is severe.

  1. State the causes, treatments and prevention of myocardial infarction?

Ans. Myocardial infarction:

The term myocardial infarction is derived from myocardium (the heart muscle) and infraction (tissue death). It is more commonly known as a heart attack and is a medical condition that occurs when the blood supply to a part of the heart is interrupted and leads the death of some cells of heart muscles.

Heart attack may be caused by blood clot in coronary arteries. It is a medical emergency, and the leading cause of death for both men and women all over the world. Severe chest pain is the most common symptom of myocardial infarction and is often described as a sensation of tightness, pressure, or neck, right arm, and back. Loss of consciousness and even sudden death can occur in myocardial infraction.


Immediate treatment for suspected acute myocardial infraction includes oxygen supply, aspirin, and sublingual tablet of glyceryl tri-nitrate.

Most cases of myocardial infarction are treated with angioplasty (mechanical widening of a narrowed or totally obstructed blood vessel) or bypass surgery (surgery in which arteries or veins from elsewhere in the patient’s body are grafted to the coronary arteries to improve the blood supply to heart muscles). Risk factors for atherosclerosis are generally risk factors for myocardial infarction.

Myocardial infarction in Pakistan:

According to a survey cardiovascular disorders were reported as the cause of 12% of the adult deaths in Pakistan (source: federal bureau of statistics of Pakistan).

Hypertension (blood pressure higher than normal) is the most common risk factor of cardiovascular disorders in Pakistan and there are over 12 million hypertension patients in Pakistan. Pakistan is among the top 10 world nations for high numbers of people with diabetes. About 10% of our population is diabetic. According to the world health organization, in Pakistan 1 in 7 urban adult males is obese. Among obese people, 22% are male, 38% are females (24-44) and 40% are females (45-64 years).




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