Question

Nitrogen is present in abundance in the atmosphere, even then we obtain it from plants. Give reasons.

Answer 1

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Nitrogen is present in the atmosphere but it is not present in the right form and we cannot make use of it. It is through plants that the right form of nitrogen is made available to us through the process of nitrogen-fixing.

Answer 2

Answer:

Because nitrogen in N2 form can not be utilized directly by eukaryotic organisms, only few prokaryotic organisms can utilize it with help of nitrogenase enzyme.

Also, the nitrogen is then to be converted to ammonia and subsequently to nitrate and nitrite in the soil with help of certain bacteria and after that plant is able to obtain it.

Plants are autotrophs and are much essential part of nutrient cycle while humans are heterotrophs who has to depend on autotrophs in direct or indirect way through the food web.