NOTES: SCIENCE(old) CLASS 8 PUNJAB TEXT BOOK BOARD LAHORE PAKISTAN 2014

(b) Can be observed with electron microscope

(c) They are of different shapes

(d) They can reproduce

(c) 71°C for half an hour (d) 100°C for one minute

The systematic grouping of organisms into categories on the basis of evolutionary or structural relationships between them; taxonomy.

SPECIES:

A fundamental category of taxonomic classification, ranking below a genus or subgenus and consisting of related organisms capable of interbreeding.

2.    Influenza

3.    Cold

4.    Small pox

5.    Polio

b-    Whooping cough

c-    Diphtheria

d-    Typhoid

e-    Pneumonia

The process in which food and other things are preserved by heating from 120°C to 126°C for 12 – 90 minutes under suitable pressure and makes the food free from pathogens.

PASTEURIZATION:
The process in which milk is heated for half an hour at 62Qc or for 15 seconds at 71 “c to make it free from bacteria.

1-    To classify means to put things into groups.

2-    Classifications systems make communication in science easier by having just one name for each organism.

3-    It also helps to organize information about organisms and their needs.

4-    Keeps scientist from giving two different names to an organism.

5-    A classification system lists organisms in a series of groups;

Kingdom, phylum, class, order, family, genus and species.

Micro means small and organisms means living things.

Micro-organisms are those organisms that are so small and they cannot be seen with naked eye.

In order to observe them, we need a light microscope or an electron microscope.

Micro-organism form diverse group which includes different kinds of organisms, viruses, plants and animals, certain algae and some fungi.

Micro-organisms differ from one another with regard to structure and mode of nutrition.

FOR EXAMPLE:

1-    On the basis of structure viruses are not cellular while other micro-organisms are cellular.

2-    Bacteria are unicellular but they have no organized nucleus while other micro-organisms have organized nucleus.

3-    According to mode of nutrition algae and a few bacteria are autotrophs while fungi and most unicellular animals are heterotrophs.

Due to these characteristics micro-organisms form a diverse group which includes different kinds of living organisms.

2-    Ferns possess vascular tissues i.e. xylem and phloem.

             Algae are the simplest group of plant kingdom. They are found in fresh water and seas. As regards to structure, algae are both unicellular and multi-cellular. Cells of algae contain nucleus
and other structures. Algae are autotrophs.

Examples: Chlamydomonas and spirogyra.

FUNGI:

Fungi are composed of numerous thread like structures (hyphae). According to mode of nutrition, fungi are hetrotrophs. They decompose dead organic matter. Few fungi causes diseases like Athletes foot and king worm in men.

Examples: Rhyzopus and mushrooms.

MOSSES:

Mosses are found in cool, moist and shady places. They live both in water and on land.
Mosses have only roots, stem and leaves structures instead of them. Vascular tissues are absent in mosses.

Examples: Polytrichum and Funeria.

FERNS:

They are adopted to live in cold, shady and humid places. They have well-developed roots stems and leaves. Vascular tissues present in ferns.

Examples: Drypteris, Pteris and Adiantum.

CONIFERS: (Evergreen)

Conifers are found in colder regions and hilly areas. They have prominent roots, leaves and stem. The leaves are long, narrow and needle like.

Seeds of conifers are present in the form of a cone. Vascular tissue (zylem &phloem) are present in them.

Examples: Deodar, Pines, Saroo and Thuja{Moor Punkh)

HABITANT:

These plants are formed in plains and can adapt to all types of environment.

STRUCTURE:

Flowering plants are found in the form of herbs, shrubs and trees.

CLASSIFICATION of FLOWERING PLANTS:

Flowering plants are divided into two groups on the basis of the number of cotyledons in the seed:

Dicotyledonous (Dicots)

Monocotyledon{Monocot)

DICOTS: Those plants, which have two cotyledons in the seeds are called Dicots.

Their leaves are usually broad.

Examples: Peas, Rose, Sunflower, Apple, Sarson, Mango etc.

2-   They have fleshy external ears.

Animals which cannot maintain their body temperature with respect to their environment are called cold blooded animals.

For example, Fish, amphibians and reptiles etc.

WARM BLOODED ANIMALS:

Animals which can maintain their body temperature with respect to their environment are called warm blooded animals.

For example; Birds and mammals etc.

(b)       Malarial parasite: It caused malaria in human beings

                       Flat worms are flat body like ribbon shaped e.g. liver fluke, tape worm etc.

ROUNDED WORMS:

Round worms rounded body worms having both the ends pointed e.g. Askers, hook worm etc.

SEGMENTED WORMS:

Their body is segmented e.g. earth worm, leach, aeries etc.

STRUCTURE: Body of fishes consists of three parts;

(1)Head (2) Trunk (3) Tail

FINS: Fins are present on the trunk region of their body.

SCALES: In the most cases, body of fishes is covered by slimy scales.

Examples: Shark, Rohu, and Trout

HABITANT: these animals are found in water, air and on land.

CLASSIFICATION: animals with jointed legs are classified into two sub-groups.

(a) Insects

(b) Worm (like animals)

INSECTS: Body of insects is divided into three parts;

Head, Thorax, Abdomen

Examples: Butter-fly, Grass hopper etc.

Worm (like animals): The body of these worms is segmented. On every segment, there is one or two pairs of legs are present.

Examples: Centipedes, Millipedes

(c) simplest ratio present between different atoms.

(d) all the above statements are true.

(i) NH₄CI (ii)H₂S0₄ (iii)Fe₂ (S0₄)₃ (iv) Ca₃(PO₄)₂

(iii)Fe₂ (S0₄)₃ =7

(iv) Ca₃(PO₄)₂=6

Carbonate, Nitrate, Hydrogen carbonate, Sulphate, Phosphate, Chloride, Copper, Sodium, Ferrous, Chromium, Silver, Magnesium.

Ammonium chloride, Aluminium phosphate, Calcium nitrate, Sodium phosphate, Barium carbonate, Zink chloride, Ammonia, Methane.

The bond formed by transference of one or more electrons from one atom to another atom is called an ionic bond.

Example:

Sodium atom transfers one of its electrons to chlorine atom and as a result, sodium ion (Nacl) and chloride ion (CI¹-) are formed.

N a————– N a + + e

Sodium atom Sodium ion

CI+ e ——-Cl-

Calcium atom——-Calcium ion

Na + +cr———- Na Cl

             The force of attraction which hold the atoms together by mutual sharing of electrons.

HYDROGEN–A COVALENT BOND:

Hydrogen gas exists in the form of diatomic molecules. Two hydrogen atoms in every hydrogen molecule are held together by mutual sharing of electrons. This mutual sharing of electrons is shown as follows:

H. + x H –. H» H –. H – H

The pair of electrons which exist between hydrogen atoms is known as shared pair of electrons.

Methyl orange, Phenolphthalein, Blue litmus

•                Blue litmus red

•                Methyl orange solution red

•           Phenolphthalein colourless

A base is a chemical species that donates electrons or hydroxide ions or that accepts protons.

Base is compound whose molecule is made up of one or more hydroxyl groups (OH^–) attached to the atom of the metal.

Citric acid, Tartaric acid, Acetic acid

Red litmus, Phenolphthalein, Methyl orange

•                Red litmus blue

•                Methyl orange solution yellow

•                 colourless Phenolphthalein pink

Coke

Charcoal

lamp black

The property by virtue of which an element exists in m0re than 0ne forms is called allotropy

-The depth of vessel

-The surface area of containing vessel

             Characteristics of liquid pressure as follows:

1. Pressure exerted increase with the depth of liquid

2. Pressure at all points at equal depth is equal

3. Liquid exerts pressure on the wall of the container.

4. Pressure exerted is directly related to its density.

5. Pressure exerted on liquid is transmitted equally in all directions. (Pascal’s law)

A ray parallel to the principal axis after refraction from lens passes through its principal focus.

A ray passing through the principal focus after refraction becomes parallel to the principal axis.

A ray passing through the optical centre of the lens goes straight without changing direction.

A lens which is thin at the middle and thick at the edges is called convex lens.

In this process diagram is drawn geometrically and then image is traced from the diagram. In ray diagram, rays of light are represented by straight lines

(c) chemical energy into electrical energy

(d) heat energy into electrical energy

The difference in electric potential between two points in an electric field; the work that has to be done in transferring unit positive charge from one point to the other. It is measured in volts. Its Symbol is U ΔV, Δφ Abbreviation pd. It is also called voltage.

EXPLAINATION:

Potential difference is like an electrical pressure difference, which pushes the4 electrons in a conductor. A source of electricity such as cell or battery provides the potential difference across a conductor. The positive terminal of the battery is said to be at higher potential and the negative terminal at lower potential.

Potential difference is measured in volts.

Hydro power systems convert this potential energy into kinetic energy in a turbine, which drives a generator to produce electricity. The greater the height and the more water there is flowing through the turbine, the more electricity can be generated.

The amount of electricity a system actually generates also depends on how efficiently it converts the power of the moving water into electrical power.

PROCESS:

Water is stored in a lake or reservoir at a height behind the dam. When water is allowed to fall from the height, it gains kinetic energy due to motion. Kinetic energy of the moving water flowing through the tunnels is used to turn the blades of turbines. These are attached to the lower end of the axil of the electric generator. The generator produces electricity which is supplied to the consumers through power stations.

Hydal power is low cost and produces no pollution.

The most common use of it is in the electric generator.

EXPLAINATION:

Electromagnetic Induction was originally discovered in 1802 by Hans Orsted.

A decade later, Michael Faraday, observed that when a electric current runs through a wire, it creates a magnetic field around that wire.

Electromagnetic Induction Works on Faraday’s Laws of electromagnetic induction. Changing magnetic flux produces current in the wire. Similarly changing voltage produces magnetic field.

ACTIVITY:

Connect a long coil of wire in series with a galvanometer.
Take a bar magnet. Push it speedily into the coil pointing its north pole toward the coil. Keep observing the needle of galvanometer carefully while pushing in the magnet.

This phenomenon is called Electromagnetic Induction.

According to this theory, about 14 billion years ago, when the entire Universe was contained in a single point in space. The Universe must have been born in this single violent event which came to be known as the “Big Bang.”

A nebula (Latin) is an interstellar cloud in outer space that is made up of dust, hydrogen and helium gas, and plasma.

It is formed when portions of the interstellar medium collapse and clump together due to the gravitational attraction of the particles.

A group of stars forming a pattern that is traditionally named after its apparent form.

There are 88 groups of stars as seen from the earth.      For example: Leo, Great Bear etc.

An area of space-time with a gravitational field so intense that its escape velocity exceeds the speed of light.

FORMATION:

If the mass of the core of star is three times bigger that mass of the Sun, then the core of star is contracts in such a way that too much density comes on one point. It is called black hole.

A comet that is not near the Sun consists only of a solid core of frozen water, frozen gases, and dust.

When a comet comes close to the Sun, it releases a gaseous tail (coma).