Nitrogen Cycle
Nitrogen circulates through Earth’s environment in several forms. Nitrogen is essential to life on Earth. Seventy-eight percent (78%) of the Earth’s atmosphere is nitrogen gas. But most of this nitrogen is not usable by life on Earth. Microscopic organisms called microbes transform nitrogen into a form usable by plants. The plants, in turn, supply nitrogen for animals. Nitrogen fixation is a process in which special bacteria and blue–green algae change nitrogen gas into certain nitrogen compounds. Lightning, ultraviolet radiation and electrical equipment can fixate nitrogen. Algae and other more complex plants use nitrates and ammonia created by nitrogen fixation. Animals eat these plants and use the nitrates in their bodies. The remains of dead plants and animals are decomposed, creating ammonia. This ammonia is a turned back into nitrate by bacteria through a process called nitrification. In watery soils, bacteria use nitrates and nitrogen gas is formed.
How many paths does nitrogen follow in the diagram?
credit: Amy Todd