Final answer:
The nitrogen cycle is a biogeochemical cycle that includes processes such as nitrogen fixation, nitrification, decay, and denitrification, all mediated by microorganisms, to move nitrogen through various forms in the ecosystem.
Step-by-step explanation:
The Nitrogen Cycle Explained
The nitrogen cycle is a biogeochemical cycle through which nitrogen is converted into various chemical forms as it circulates among the atmosphere, terrestrial, and aquatic ecosystems. The main processes of the nitrogen cycle include nitrogen fixation, nitrification, decay, and denitrification. These processes are primarily mediated by microorganisms.
Nitrogen Fixation
Nitrogen fixation is the process by which nitrogen in the atmosphere (N₂) is converted into ammonia (NH₃) by nitrogen-fixing bacteria, either free-living or symbiotic bacteria, such as those found in the roots of legumes. Ammonia can then be converted to ammonium (NH₄⁺), which plants can assimilate.
Nitrification
Nitrification is the conversion of ammonium to nitrite (NO₂⁻) and then to nitrate (NO₃⁻) by bacteria, making nitrogen available to plants in a form they can use.
Decay
During decay, decomposing bacteria and fungi break down dead organisms and other organic matter, releasing ammonium back into the soil.
Denitrification
Denitrification is the reduction of nitrates back to the gaseous form of nitrogen (N₂), which is then released back into the atmosphere, completing the cycle.
The cycle is essential for replacing the nitrogen that plants and other organisms use to create important organic molecules like proteins and nucleic acids. Without this cycle, ecosystems would run out of usable nitrogen.