Nitrogen cycle

Definition

The nitrogen cycle is a biogeochemical process by which nitrogen is converted into various chemical forms as it circulates among the atmosphere, terrestrial, and marine ecosystems. Microorganisms play a crucial role in facilitating the different stages of this cycle.

5 Must Know Facts For Your Next Test

1. Nitrogen fixation is the process where atmospheric nitrogen (N2) is converted into ammonia (NH3) by certain bacteria.
2. Nitrification involves the conversion of ammonia to nitrites (NO2-) and then to nitrates (NO3-) by nitrifying bacteria.
3. Denitrification is the reduction of nitrates back into gaseous nitrogen (N2), primarily performed by anaerobic bacteria.
4. Ammonification is the decomposition of organic nitrogen into ammonia by decomposer microorganisms.
5. Certain microorganisms, such as Rhizobium, form symbiotic relationships with leguminous plants to fix atmospheric nitrogen.

Review Questions

• What role do nitrifying bacteria play in the nitrogen cycle?
• Describe the process of denitrification and its significance.
• How do microorganisms contribute to the nitrogen fixation process?

Related terms

Nitrogen Fixation:

Conversion of atmospheric nitrogen into ammonia by specific bacteria.

Nitrification: Process of converting ammonia into nitrites and then into nitrates.

Denitrification:

Reduction of nitrates back into gaseous nitrogen by anaerobic bacteria.