Exercise:
Q1. Why is the atmosphere essential for life?
Ans: Atmospher is very essential for life because of following reasons;
(i) It keeps the avearge temperature of earth rather steady.
(ii) Oxygen is available from atmosphere in the form of life air.
(iii) Ozone layer of our atmosphere protect us from harmful radiation coming from the sun.
Q2. Why is water essential for life?
Ans: Water is essential for life because;
(i) All cellular processes take place in a water medium.
(ii) All the reactions that take place within our body and within the cells
occur between substances that are dissolved in water.
(iii) Substances are also transported from one part of the body to the
other in a dissolved form.
(iv) organisms need to maintain the level of water within their bodies in
order to stay alive.
Q3. How are living organisms dependent on the soil? Are organisms that live in water totally independent of soil as a resource?
Ans: Living organisms dependent on soil because;
(i) Soil is an important resource that decides the diversity of life in an area.
(ii) The minerals found in this upper layer (Crust) supply a variety of nutrients to life-forms.
(iii) Soil also contains various forms of microscopic life and they get their all forms of need from soil.
(iv) All green plants grow in soil those are used as food energy by animals.
Q4. You have seen weather reports on television and in newspapers. How do you think we are able to predict the weather?
Ans:
Q5. 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?
Ans:
Q6. Write a note on how forests influence the quality of our air, soil and water resources.
Ans:
(i) Forests is one of the most important natural resource. Forests also keep balance between carbon dioxide and oxygen. They take CO2 for photosynthesis and release oxygen from this process. In another process called respiration they take O2 and release CO2.
(ii) Forests prevent soil erosion. the roots of plants hold soil tightly and prevent thier removal by water and wind. Their dead and decay leaves form humus for soil and gain fertility.
(iii) Forests play an important role in maintaining water cycle by transpiration. In the process of transpiration they release water vapour.
