Air consists of various gaseous substances, e.g. oxygen, nitrogen, carbon-dioxide, hydrogen, ozone, argon, helium etc. Among these, oxygen and nitrogen are the chief constituents of the air. Besides these, there is a little amount of water vapor.
The important abiotic component of the environment directly or indirectly influences the living organisms. Without air, living organisms have no existence. Almost all living organisms, plants and animals require oxygen, more or less, for their respiration. Besides this, fire is extinguished in absence of oxygen, and without fire, the life style of man becomes disrupted.
During respiration, the living organisms take oxygen and release carbon-dioxide in their surroundings. Green plants utilize this carbon-dioxide during daytime in presence of sunlight to prepare their carbohydrate food inside the green leaves. While doing so, they release oxygen in their surroundings. Green plants do this work in daylight. In this way, a perfect balance of oxygen and carbon-dioxide is maintained in the nature.
On the other hand, no plant or animal is capable of taking nitrogen directly from the air, although about half of the dry weight of an organism is made up of nitrogenous constituents, i.e., it is an essential component required to form the cell structure of living organisms. Nitrogenous compounds are absorbed from the soil by the plants through their roots and are converted to the body constituents and are utilized to form the cell structure. All animals get their nitrogen supply directly or indirectly from these plants. Animals generally collect this nitrogen from protein foods.
Due to lightning, the atmospheric oxygen and nitrogen react with each other and as a result of this, nitrogenous compounds are formed. These compounds ultimately mix with the soil with the rainfall and nitrogen, in these forms, is absorbed by plants through their roots from the soil.