Question

Why does the percentage of gases like oxygen, nitrogen and carbon dioxide remain almost the same in the atmosphere?

Answer 1

Hint:-Each and every organism needs a constant supply of nutrients to grow, reproduce and regulate various body functions. The amount of minerals varies in different ecosystems but the amount of gases remains constant. Nutrients are never lost from the ecosystems and are recycled time and again indefinitely. The movement of nutrient elements through various components of an ecosystem is called a biogeochemical cycle.

Complete Answer:-
The biogeochemical cycles are of two types- gaseous cycles and sedimentary cycles. Gaseous cycles include nitrogen cycle, oxygen cycle and carbon dioxide cycle mainly while sedimentary cycles include sulphur cycle and phosphorus cycle. Main reservoirs of carbon are the atmosphere, oceans, carbonate rocks, coal and petroleum. The carbon released from them is present in the atmosphere in the form of carbon dioxide. This carbon dioxide is then used by plants for photosynthesis. Animals then consume these plants and ultimately release carbon dioxide into the atmosphere by respiration.
During the nitrogen cycle, atmospheric nitrogen is first fixed to form ammonia. Then, this ammonia is converted to nitrates and nitrites by specific bacterias. Then, denitrification of these products takes place and ultimately nitrogen moves into the atmosphere.
Green plants use atmospheric carbon dioxide for photosynthesis. During photosynthesis, oxygen is released by the plants into the atmosphere. This oxygen is then further utilised by microbes and animals. They release carbon dioxide through respiration and this carbon dioxide is again utilised by plants for photosynthesis.
Thus due to this cyclical flow of gases their percentage remains almost the same in the atmosphere.

Note:- The reservoir for gaseous type of nutrient cycle exists in the atmosphere and for sedimentary cycle, the reservoir is located in the earth's crust. The function of a reservoir is to meet with the deficit which occurs due to imbalance in the rate of influx and efflux. The proper functioning of biogeochemical cycles is very essential for the maintenance of a healthy ecosystem.