Natural Resources – Air, Water and Land
Exercise
1. Fill in the blanks:
(a) The layer of ozone gas absorbs ultraviolet rays that come from the sun to the earth.
(b) Of the total water available on the earth, fresh water forms 2.7 percent.
(c) Both biotic and abiotic constituents are present in the soil.
2. Why is it said that – ?
(a) The ozone layer is a protective shell of the earth.
Answer – The ozone layer absorbs harmful ultraviolet rays from the sun, which can be dangerous to living beings. This protects all life on Earth.
(b) Water is life.
Answer – All living things need water to survive. It is necessary for drinking, farming, cooking, and cleaning. Without water, life cannot exist.
(c) Seawater is useful even though it is not potable.
Answer – Seawater is used for fishing, transportation, and producing salt. It also helps in maintaining the water cycle by forming clouds through evaporation.
3. What will happen if – ?
(a) Microbes in the soil get destroyed.
Answer – The soil will lose its fertility as microbes help decompose dead plants and animals, making the soil rich in nutrients.
(b) The number of vehicles and factories in your surroundings increases.
Answer – Air pollution will increase, leading to health problems like breathing difficulties and global warming.
(c) The total supply of potable water is finished.
Answer – People and animals will struggle to survive, agriculture will fail, and life on Earth will be in danger.
4. Match the following:
1. Carbon dioxide → (c) Plants and food production
2. Oxygen → (d) Combustion
3. Water vapour → (b) Rain
4. Microbes → (a) Generation of soil
5. Name the following:
(a) Constituents of the biosphere → Air, water, land, and living organisms.
(b) Biotic constituents of soil → Microbes, insects, worms, rodents.
(c) Fossil fuel → Coal, petroleum, natural gas.
(d) Inert gases in air → Argon, Neon, Krypton, Xenon, Helium.
(e) Gases that are harmful to the ozone layer → Chlorofluorocarbons (CFCs), Carbon tetrachloride.
6. True or false?
(a) Land and soil are the same thing. → False
(b) The water in a lake is called groundwater. → False
(c) It takes about 1000 years to form a 25 cm thick layer of soil. → False (It takes 1000 years to form a 2.5 cm layer of soil.)
(d) Radon is used in decorative lights. → 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.
Answer – Soil is formed by the breaking down of rocks due to wind, water, and temperature changes. The process is slow and takes thousands of years. Microbes and dead plant material also contribute to soil formation.
(b) Why is there a shortage of water even though it occupies about 71% of the earth’s surface?
Answer – Most of the Earth’s water (97%) is salty and found in oceans. Only a small amount (2.7%) is fresh water, and an even smaller portion is available for human use, as much of it is frozen in glaciers or deep underground.
(c) What are the various constituents of air? Write their uses.
Answer – Nitrogen (78%) → Helps in plant growth and protein formation.
Oxygen (21%) → Essential for breathing and burning.
Carbon dioxide (0.03%) → Used by plants for photosynthesis.
Argon (0.9%) → Used in electric bulbs.
Neon, Krypton, Xenon → Used in lights and photography.
(d) Why are air, water, and land considered valuable natural resources?
Answer – These resources are necessary for the survival of all living beings. Air provides oxygen, water is needed for drinking and farming, and land supports human settlements and agriculture. They must be used wisely to ensure sustainability.
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