AP BIOLOGY

Detailed explanation-1: -Denitrification is the process that converts nitrate to nitrogen gas, thus removing bioavailable nitrogen and returning it to the atmosphere. Dinitrogen gas (N2) is the ultimate end product of denitrification, but other intermediate gaseous forms of nitrogen exist (Figure 7).

Detailed explanation-2: -Denitrifying bacteria convert the nitrate back into nitrogen gas, which reenters the atmosphere. Nitrogen from runoff and fertilizers enters the ocean, where it enters marine food webs. Some organic nitrogen falls to the ocean floor as sediment.

Detailed explanation-3: -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.

Detailed explanation-4: -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-5: -Denitrification is the reduction of NO3-to gaseous N2 by anaerobic bacteria. This process only occurs where there is little to no oxygen, such as deep in the soil near the water table. Hence, areas such as wetlands provide a valuable place for reducing excess nitrogen levels via denitrification processes.