Published on
Scene 1 (0s)


Scene 2 (10s)

Fill in the blanks:. The layer of ozone gas adsorbs __________ rays that come from the sun to the earth. ANSWER: Ultra violet rays (u.v.rays) b. Of the total water available on the earth, fresh water form ________ percent. ANSWER: 0.3%.

Scene 3 (27s)

C. Both ______and ______ constituents are present in the soil. ANSWER: biotic, abiotic.

Scene 4 (36s)

Why is it said that-. The ozone layer is a protective shell of earth. ANSWER: 1 The ultra violet (u.v) rays coming from the sun are very harmful for living things. 2. The ozone gas absorbs these rays. 3. As a result, life on earth is protected..

Scene 5 (53s)

Question 3: Seawater is useful eventhough it is not potable: Answer: 1. Many fish and aquatic animals live in sea water. 2. The water from the sea evaporates to form clouds and it brings rains. 3. The sea water aslo helps the land to cool due to breezes. 4. The salt and minerals are also obtained forms sea water. 5. Corals and pearls are obtained from sea animals. 6. Thus seawater is useful eventhough it is not potable..

Scene 6 (1m 18s)

Question 2 :. Water is life : Answer : 1.Water is a good solvent and it dissolves many substances. 2.The human blood is made of 70% water and the sap of plant also contains a very high proportion of water. 3. As the life processes would not take place in the absence of water. Hence without water, no living organism can survive. 4.There fore, we could say that “Water is Life ‘.

Scene 7 (1m 41s)

What will happen if-. a. Microbes in the soil get destroyed. Answer : Humus is the layer formed on the soil due to the decomposition of dead animals by microbes . Humus supplies nutrients to the soil. Humus is also important for aerating the soil and for holding water in the soil. The proportion of humus in the good fertile soil is about 33% to 50%. If microbes are destroyed, humus will not be formed and the soil will not become fertile. Plants will not grow and decomposition of leaves and animals will not take place and it will accumulate on the land..

Scene 8 (2m 9s)

The number of vehicles and factories in your surroundings increases.

Scene 9 (2m 35s)

C. The total supply of the potable water is finished :.

Scene 10 (2m 59s)

Match the following :. Question A :. Group A Carbon dioxide Oxygen Water vapour Microbes Group B Generation of soil Rain Plants and food production combustion.

Scene 11 (3m 16s)

5. Name the following :. Constituents of the biosphere Answer: All living things on earth, the parts of the lithosphere, hydrosphere and atmosphere are the constituents of the biosphere. Biotic constituents of soil : Answer : The biotic constituents of soil are microbes, worms, insects, rodents like mice and rats, roots of trees and plants..

Scene 12 (3m 34s)

C. fossil fuel : Answer: Crude oil is a fossil fuel. We get fuels like petrol, kerosene, diesel, paraffin and other useful materials like tar and wax from crude oil. D. inert gases in air : Answer : Inert gases in air are Neon, Argon, Helium, Krypton and Xenon..

Scene 13 (3m 52s)

e . Gases that are harmful to the ozone layer : Answer : The gases that are harmful to the ozone layer are carbon tetrachloride or the chlorofluorocarbons used in airconditioners and refrigerators mix with the air..

Scene 14 (4m 5s)

6. True or false. Land and soil are the same thing. Answer: False : land is seen in the form of stones, soil and big rocks. Soil is a form of land. b.The water in a lake is called ground water . Answer: False : the water trapped below the ground over the bedrocks is called ground water. c . it takes about 1000 years to form a 25cm thick layer of soil. Answer: False : The process of soil formation is slow and continuous. It takes about a thousand years for a 2.5cm thick layer of mature soil to form..

Scene 15 (4m 33s)

d . Radon is used in decorative lights. Answer : False : Neon is used in decorative lights and for street li ghting..

Scene 16 (4m 44s)

7. Answer in your own words. Explain with the help of a diagram how soil is formed : Answer : F ormation of soil :.

Scene 17 (5m 4s)

. Why is there a shortage of water even though it occupies about 71% of the earth’s surface. Answer: we cannot use all the water on earth because sea water is salty(97% water available on earth is sea water). Some water is in the frozen state, ground water (2.7% water available on earth) A very small quantity of water is available for drinking.(0.3% water available on earth) Due to the uncontrolled use of water for an increasing population, industry, industry and farming, it is now in short supply. Therefore, water scarcity is a serious problem..

Scene 18 (5m 31s)

C. what are the various constituents of air? Write their uses?.

Scene 19 (5m 56s)

* c . carbon dioxide(0.03%) : plants use it for producing their food. Used in fire extinguishers d. Inert gases (0.9%) Argon : used in electric bulbs Helium : used for obtaining low temperature and also generating lifts in airships Neon : used in decorative lights and for street lighting Krypton : used in fluorescent tubes. Xenon : used in flash photography ` e. Other constituents like dust particles and water vapour (0.7%) : Used in formation of cloud, fog dew etc. spread sunlight in all directions..

Scene 20 (6m 21s)

d . Why are air, water and land considered to be valuable natural resources?.

Scene 21 (7m 3s)