Toxic or Not Image Map
Welcome to Your WorldLesson Guide image map

The Chemical Cycles

The Nitrogen Cycle
Organisms require nitrogen to produce amino acids. Nitrogen makes up seventy-eight percent of the atmosphere, but most organisms can not use this form of nitrogen, and must have the fixed form. The nitrogen cycle produces the fixed form of nitrogen these organisms need.

Illustration of the Nitrogen CycleStep 1:  A special type of bacteria called nitrogen fixing bacteria take in atmospheric nitrogen and produce ammonia (NH3).

Step 2:  Other bacteria use this ammonia to produce nitrates and nitrites, which are nitrogen and oxygen containing compounds.

Step 3:  The nitrates and nitrites are used by plants to make amino acids which are then used to make plant proteins.

Step 4:  Plants are consumed by other organisms which use the plant amino acids to make their own.

Step 5:  Decomposers convert the nitrogen found in other organisms into ammonia and return it to the soil. A few of these type of bacteria return nitrogen to the atmosphere by a process called denitrification, however this amount is small.

Back to previous pageNext Page