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

What is the role of the atmosphere in climatic control?

Every gas undergoes a cyclic process in the atmosphere wherein these gases are used and released by various organisms through different processes. The consistency maintained in the cycling of these gases leads to almost same percentage of these gases in the atmosphere.

Role of atmosphere in climate control:

The atmosphere keeps the average temperature of earth almost same during the daytime in whole year.It prevents the sudden increase in temperature during daytime while it slows down the escape of heat during night into the outer space.In this way it doesnot let climate become too cool during night.