AP BIOLOGY

Detailed explanation-1: -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: -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-3: -Rhizobium bacteria present in the roots of leguminous plants absorb atmospheric nitrogen and convert it into nitrogen compounds.

Detailed explanation-4: -Pseudomonas bacteria convert nitrates into nitrogen gas.

Detailed explanation-5: -Ammonification is the conversion of organic nitrogen into ammonia. The ammonia produced by this process is excreted into the environment and is then available for either nitrification or assimilation.