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Why is the atmosphere essential for life?


The atmosphere consists of gases like nitrogen, oxygen, carbon dioxide and water vapour. All these gases are very essential for the survival of organisms. The atmosphere keeps the average temperature of the earth fairly steady and thus makes conditions suitable for the survival of organisms. The atmosphere prevents the sudden increase in temperature during the daylight hours. It also slows down the escape of heat into outer space during the night, keeping the Conditions favourable. Because of all these reasons atmosphere is very important. 

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How are living organisms dependent on the soil? Are organisms that live in water totally independent of soil as a resource?


Living organisms directly or indirectly are dependent on soil. Because for substances and energy (food) all living things depend on green plants. Carnivores (which eat other animals) also depend on animals which eat plants. Plants need soil for their survival. Because soil provides the following things to the plants:

(i) nutrients (minerals) to prepare food through photosynthesis for self and other organisms.

(ii) support.

Thus, ultimately all living organisms are dependent on the soil.

It is not true to say that organisms that live in water are totally independent of soil as a resource. Organisms living in water depend on green plants for materials and energy. Aquatic green plants get dissolved mineral from water. Water bodies get supply of minerals from the soil through rivers, rain water, etc. The minerals locked in rocks cannot be available to organisms until rocks are converted to small particles of soil. If there is no continuous supply of mineral from the soil to water bodies, minerals present in the water will exhaust. The organisms living in water will not be able to survive for a long time. Thus, organisms that live in water are not totally independent of soil as a resource.

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You have seen weather reports on television and in newspapers. How do you think we are able to predict the weather?


Prediction of the weather can be done by studying wind patterns which decide rainfall patterns. It also shows areas of low pressure and high pressure. these areas give an idea about the rainfall patteren of the area. For example in large part of India, rains are mostly brought by the South-West or North-East monsoons. This is how the weatherof the area is predicted taking into account the wind pattern. 

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Why is water essential for life?


Water is essential for life because

(i) all life processes that take place in the cells require water medium.

(ii) water is needed for transportation of substances from one part of the body to the other in a dissolved form.

(iii) All the reactions in the body or within the cells occur between substances that are dissolved in water.

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What are the two forms of oxygen found in the atmosphere?


Oxygen is found in the atmosphere in the form of

(i) a diatomic molecule having two atoms of oxygen, with chemical formula O2.

(ii) a triatomic i.e., containing three atoms of oxygen, with a chemical formula O3, called ozone.

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