Why is the atmosphere essential for life ?SOLUTION:
Atmosphere is very important for sustaining life:
(i) It contains various gases like O2, CO2, N2 which are required for various life processes by plants and animals.
(ii) CO2 gas is used by plants to prepare food by the process called photosynthesis.
(iii) Oxygen is required for burning, combustion and respiration.
(iv) Ozone layer is acting as a protective layer which avoids/prevents harmful U.V. rays to enter the Earth’s atmosphere.
(v) Atmosphere acts as a temperature buffer.
Why is water essential for life?SOLUTION:
(i) About 70% weight of human being is due to water.
(ii) All cellular processes take place in water as medium.
(iii) All reactions taking place within our body cells involve substances that are dissolved in water.
(iv) Transportation of substances from one part of the body to another takes place in dissolved form.
(v) Terrestrial life-forms require fresh water to get rid of high amounts of wastes.
How are living organisms dependent on the soil? Are organisms that live in water totally independent of soil as a resource?SOLUTION:
All living organisms are directly or indirectly dependent on soil. Plants obtain water, minerals from the soil and prepare food for animals.
Other organisms that live in water are not totally independent of soil because the plants growing on the soil in water are the primary producers which start the food chain and even the microbes that live in soil help in the decomposition of dead plants and animals in water to return the nutrients back to the water.
You have seen weather reports on television and in newspapers. How do you think we are able to predict the weather?SOLUTION:
We daily see weather reports on televisions and newspapers. These informations are actually recorded by meteorological laboratories present in different cities of the country. Information such as direction and speed of wind, average daily minimum and maximum temperature, relative humidity, patterns of cloud formation, depression zone over an area etc., are recorded with the help of instruments and then displayed on television or published in newspapers. This meteorological information helps us to predict the weather.Q 5.
We know that many human activities lead to increasing levels of pollution of the air, water-bodies and soil. Do you think that isolating these activities to specific and limited areas would help in reducing pollution?SOLUTION:
If the human activities which lead to increasing level of air, water and soil pollution is spread in wider area then the pollutants will spread more, but yes, if it is limited and confined to a place then the soil and water pollution can be controlled, to some extent air-pollution can also be minimised.Q 6.
Write a note on how forests influence the quality of our air, soil and water resources?SOLUTION:
Role of forest in influencing the quality of
(a) Air :
(i) It helps in purifying the air by adding oxygen into it.
(ii) It takes carbon dioxide gas during photosynthesis thus greenhouse effect is controlled.
(iii) Transpiration helps in the formation of clouds and thus, it maintains the temperature of surrounding area, giving cooling effect.
(b) Soil :
(i) Plants in forest hold the soil thereby preventing soil erosion.
(ii) Trees in the forest do not allow the rainwater to hit the floor directly. Rain water comes down slowly through leaves and stems of plants. Hence forests allow percolation of rainwater to deep layers which helps in increasing the underground water level.
(c) Water : Forest helps in bringing rain and increasing the level of water in the underground and water bodies.