Natural Resources - Air, Water and Land | Class 6 | Science | Chapter 1 | Maharashtra State Board
In this educational video, viewers will gain a better understanding of the natural resources that are essential for life on earth. The video will cover the composition of the air we breathe, including the proportions of various gases such as nitrogen, oxygen, carbon dioxide, argon, helium, neon, krypton, and xenon. It will also highlight the important role these gases play in our daily lives. The video will then shift focus to air pollution, discussing harmful substances that are released into the air and the importance of the ozone layer. Moving on to the topic of water, viewers will learn about the distribution of water on our planet and the crucial role it plays in our lives. Finally, the video will discuss the land we live on, exploring its composition and the process of soil formation. This video is a great resource for anyone seeking a comprehensive understanding of the natural resources that sustain life on earth.
Questions & Answers
1. Fill in the blanks.
The layer of ozone gas absorbs ultraviolet rays that come from the sun to earth.
Of the total water available on the earth, fresh water forms 0.3 percent.
Both biotic and abiotic constituents are present in the soil.
2. Why is said that?
(a) The ozone layers is a protective shell of the earth.
Ans.
The ultra violet (UV) rays coming from the sun are very harmful for living things.
The ozone layer present in the lower stratosphere absorb this UV rays and prevent them from reaching the earth. As a result life on earth is protected.
Therefore, it is said that the ozone layer is a protective shell of the earth.
(b) Water is life.
Ans.
Water is a good solvent and it dissolves many substances.
The human blood is made of 70% water and the sap of plant also contains a very high proportion of water.
All the life processes would not take place in the absence of water.
Hence, without water no living organism can survive.
Therefore, it is said that 'water is life'.
(c) Sea water is useful even though it is not potable. OR
In what way is sea water useful even though it is salty?
Ans. Thus,
Many fish and aquatic animals live in sea water.
The water from the sea evaporates to form clouds which brings rain.
The sea water also helps the land to cool due to breezes.
The salt and minerals are also obtained from sea water.
Corals and pearls are obtained from sea animals.
Thus, sea water is useful even though it is not potable.
3. What will happen if -
(a) Microbes in the soil get destroyed.
Ans.
Microbes in the soil decompose dead plants and animals and convert it into humus. This humus supplies nutrients to the soil.
Humus also aerates soil and holds water in it. It makes the soil more fertile.
If microbes are destroyed, humus will not be formed and the soil will not become fertile, making it unsuitable for growth of plants. Also dead and decaying matter will accumulate on land.
(b) The number of vehicles and factories in your surroundings increases.
Ans.
Vehicles and factories are the major cause of air pollution.
They release harmful gases like carbon dioxide, carbon monoxide and sulphur dioxide into the air.
These pollutants are harmful to the environment and to the people living in the surrounding area.
Hence, if the number of vehicles and factories in our surroundings increases, the air pollution will also increase.
(c) The total supply of potable water is finished.
Ans.
Water plays very important role in the survival of living organism.
All living things are dependent on water.
A very small quantity of water is potable and can be used for drinking.
All bodily functions are regulated by water.
Therefore, if total supply of potable water is finished, plants and animals will not survive and there will be no life on earth.
4. Match the following.
Group 'A' | Answer | Group 'B' |
Carbon dioxide | Plants and food production | Generation of soil |
Oxygen | Combustion | Rain |
Water vapour | Rain | Plants and food production |
Microbes | Generation of soil | Combustion |
5. Name the following.
(a) Constituents of the biosphere.
Ans. Atmosphere, hydrosphere, lithosphere and all living things on earth.
(b) Biotic constituents of soil.
Ans. Microbes, worms, insects, burrowing rodents like rats, mice, roots of trees and plants.
(c) Fossil fuel.
Ans. Crude oil from which we get kerosene, petrol, diesel, paraffin wax and tar.
(d) Inert gases in air.
Ans. Neon, argon, helium, krypton, xenon.
(e) Gases that are harmful to the ozone layer.
Ans. Chlorofluorocarbon and carbon tetrachloride.
6. True of false?
(a) Land and soil are the same thing.
Ans. False – Land consists of stones, soil and big rocks.
(b) The water in a lake is called ground water.
Ans. False – Water trapped below the ground over the bedrocks is called ground water.
(c) It takes about 1000 years to form a 25 cm thick layer of soil.
Ans. False – It almost takes around thousand years to form a 2.5 cm thick layer of soil.
(d) Radon is used in decorative lights.
Ans. False – Neon is used in decorative lights.
7. Answer in your own words.
(a) Explain with the help of a diagram, how soil is formed.
Ans.
The soil on the land is formed by a natural process.
The abiotic components of soil are supplied through the weathering of the bedrock.
Due to heat, cold wind and rain the bedrock breaks down into pieces.
Stones, sand and soil are formed from these pieces.
Microbes, worms, insects, rodents and roots of trees growing on land help in weathering of rocks.
This process is slow, continuous and it takes a thousand years to form 2.5 cm. thick layer of mature soil.
(b) Why is there a shortage of water even though it occupies about 71% of the earth’s surface?
Ans.
71% of earth’s surface is covered with water, of which 97% is salty water present in seas and oceans and 2.7% water is available as ground water, ice and in other forms.
Only 0.3% water is available as fresh water which can be used for drinking.
All the living organisms require water to drink. The water is used in the industry and also for farming.
Due to increasing population and uncontrolled usage, we experience shortage of water.
(c) What are the various constituents of air? Write their uses.
Ans. Air contains gases like oxygen, carbon dioxide, nitrogen, inert gases, water vapour and dust particles. The uses of constituents of air are as follows.
| Gases | Proportion in atmosphere | Uses |
1. | Nitrogen | 78% |
|
2. | Oxygen | 21% |
|
3. | Carbon dioxide | 0.03% |
|
4. | Inert Gases
| 0.9% |
|
5. | Other constituents like dust, water vapours | 0.7% |
|
(d) Why are air, water and land considered to be valuable natural resources?
Ans.
The various components of air help and support the growth of living organisms.
Nitrogen is used to make proteins, oxygen is used for respiration and carbon dioxide is used to make food by plants.
Similarly, land supports growth of terrestrial plants and animals. It provides important minerals to plants and also to human beings.
It is the shelter for worms, insects and rodents and supports their growth. Plants also cannot survive without land.
Water is necessary for carrying out all life processes in the living organisms and without water there will be no life on earth.
Hence land, air and water are considered valuable natural resources.
E X T R A
1. Answer in one sentence.
(a) What are the constituents of soil? Classify them as biotic and abiotic constituents.
Ans. The constituents of soil are humus, soil, sand, gravel, stones, bedrock, insects, worms, microbes, roots of trees and dead leaves, burrowing rodents like mice and rats.
Biotic | Abiotic |
Microbes, rodents like mice and rats, humus containing microbes and dead leaves. | Soil, sand, gravel, stones, bedrock. |
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