Air is a mixture. It contains many gases including nitrogen, oxygen and carbon dioxide. Nitrogen combines with other elements to make compounds called ‘proteins’. Proteins help plants and animals grow, and animals need oxygen to breathe. At the top of a mountain, there is less air than at the bottom. For this reason, mountain climbers sometimes need to take extra oxygen with them.
In sunlight, plants grow by combining carbon dioxide and water to produce more of the chemicals of which they are made. Gases in the air are being used all the time, but they never run out!
The Gas Cycle
We take oxygen from the air, but put back carbon dioxide. Plants take carbon dioxide from the air and, during the day, put back oxygen. Plant and animal bodies contain nitrogen. When they die, this nitrogen returns to the air or soil. Oxygen, carbon dioxide and nitrogen are constantly recycled so we never run out!
Fighter pilots take their own oxygen supply with them as there is very little air at high altitudes.
Plants and animals depend on each other to produce the chemicals needed for survival.
Picture Credit : Google