The gas composition of the atmosphere is maintained at a relatively constant level. Explain the role organisms play in this.

Air has approximately the same composition and percentage of gases. Most of all are nitrogen (78.3%), oxygen (21.5%) and carbon dioxide (0.03%). This composition is supported by the presence of living organisms, which are involved in maintaining the composition. Plants recycle the carbon dioxide that animals breathe out, as well as plankton and many bacteria. Some bacteria and animals produce carbon dioxide. Nitrogen is produced by plankton and some plants. Because of this, the composition of the air does not change for several hundred thousand years.