AP BIOLOGY

Detailed explanation-1: -Denitrification. Denitrification completes the nitrogen cycle by converting nitrate (NO3-) back to gaseous nitrogen (N2). Denitrifying bacteria are the agents of this process. These bacteria use nitrate instead of oxygen when obtaining energy, releasing nitrogen gas to the atmosphere.

Detailed explanation-2: -Nitrogen-fixing bacteria in the soil and within the root nodules of some plants convert nitrogen gas in the atmosphere to ammonia. Nitrifying bacteria convert ammonia to nitrites or nitrates. Ammonia, nitrites, and nitrates are all fixed nitrogen and can be absorbed by plants.

Detailed explanation-3: -Stage 5: Denitrification In the fifth stage of the nitrogen cycle, nitrogen returns to the air as nitrates are converted to atmospheric nitrogen (N2) by bacteria through the process we call denitrification.

Detailed explanation-4: -Nitrogen Fixation Process During the process of Nitrogen fixation, the inert form of nitrogen gas is deposited into soils from the atmosphere and surface waters, mainly through precipitation. The entire process of Nitrogen fixation is completed by symbiotic bacteria, which are known as Diazotrophs.

Detailed explanation-5: -Nitrogen is returned to the atmosphere by the activity of organisms known as decomposers. Some bacteria are decomposers and break down the complex nitrogen compounds in dead organisms and animal wastes. This returns simple nitrogen compounds to the soil where they can be used by plants to produce more nitrates.