Nitrogen is removed from the atmosphere and deposited at the Earth's surface mainly by specialized nitrogen fixing bacteria, and by way of lightning through precipitation. The addition of this nitrogen to the Earth's surface soils and various water bodies supplies much needed nutrition for plant growth. Nitrogen returns to the atmosphere primarily through biomass combustion and denitrification . Oxygen is exchanged between the atmosphere and life through the processes of photosynthesis and respiration . Photosynthesis produces oxygen when carbon dioxide and water are chemically converted into glucose with the help of sunlight.
Respiration is a process whose reciprocal is photosynthesis.
In respiration, oxygen is combined with glucose to chemically release energy for metabolism. The products of this reaction are water and carbon dioxide. The next most abundant gas on the table is water vapor . Water vapor varies in concentration in the atmosphere both spatially and temporally. The highest concentrations of water vapor are found near the equator over the oceans and tropical rain forests.