Question

The percentage of nitrogen present in the atmosphere is
A) $86\%$
B) $78\%$
C) $20\%$
D) $50\%$

Answer 1

Atmosphere is a layer of gasses which surrounds the earth and is made up of nitrogen, oxygen, argon and carbon dioxide. It consists of a very small percentage of water vapor. It helps in protecting the earth from harmful UV rays of the sun.

Complete answer:
Oxygen is required by most of the organisms for respiration and breathing.
Plants, algae and cyanobacteria use carbon dioxide for photosynthesis.
Nitrogen is used by bacteria and lighting to produce ammonia for the construction of nucleotides and amino acids.
Atmosphere protects living organisms from genetic damage by various rays like solar wind, solar ultraviolet radiation and cosmic rays.
Layers of atmosphere:
Troposphere is the lowest layer which extends from the surface to the bottom of another layer called stratosphere. Depth of this layer varies between $17\,km$ at the equator to $7\,km$at the poles.
The Stratosphere extends from the top of the troposphere to the bottom of the mesosphere (contains ozone layer).
The thermosphere extends from $85\,\,km$to the base of the exosphere at $400\,km$ and contains ionosphere.
The percentage of gases in the atmosphere are $78\%$ Nitrogen, $21\%$ Oxygen, $0.93\%$ Argon and $0.04\%$ carbon dioxide.
The correct answer is $78\%$

Note: Nitrogen is the major component of chlorophyll, pigment of plants which use sunlight to give water and carbon dioxide. It is also a major component of amino acids (building blocks of proteins).