Oxygen

Oxygen is symbolized by O₂.

The bulk of atmospheric oxygen comes from the green plants.

Oxygen is a constituent of many of our foods.

Almost all living organisms, plants and animals require oxygen for their respiration.

This oxygen is utilized by them to breakdown food materials and release stored energy from the latter.

The released energy is utilized for their existence.

During respiration carbon dioxide is also released by organism which increases carbon dioxide concentration of the air. Oxygen is also locked up with many elements of the soil as their oxides, which serve as nutrients for plants.