AP BIOLOGY

Detailed explanation-1: -Denitrification. Denitrification is the process that converts nitrate to nitrogen gas, thus removing bioavailable nitrogen and returning it to the atmosphere.

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.

Detailed explanation-3: -Denitrification is the chemical reduction of soil nitrates or nitrites by denitrifying bacteria leading to gaseous N losses. When oxygen is limited, some bacteria use nitrate to support respiration.

Detailed explanation-4: -Ammonification: Ammonification occurs when bacteria or fungi convert nitrogen gas (N2) or nitrogen compounds into ammonium ions (NH4+). Soil contains bacteria that use enzymes to convert nitrogen gas (N2) into ammonium ions (NH4+). The ammonium ions bind to soil particles.

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.