AP BIOLOGY

Detailed explanation-1: -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-2: -Biologically: Nitrogen gas (N2) diffuses into the soil from the atmosphere, and species of bacteria convert this nitrogen to ammonium ions (NH4+), which can be used by plants. Legumes (such as clover and lupins) are often grown by farmers because they have nodules on their roots that contain nitrogen-fixing bacteria.

Detailed explanation-3: -A small amount of nitrogen is fixed by lightning, but most of the nitrogen harvested from the atmosphere is removed by nitrogen-fixing bacteria and cyanobacteria (formerly called blue-green algae).

Detailed explanation-4: -Biological nitrogen fixation (BNF), discovered by Beijerinck in 1901 (Beijerinck 1901), is carried out by a specialized group of prokaryotes. These organisms utilize the enzyme nitrogenase to catalyze the conversion of atmospheric nitrogen (N2) to ammonia (NH3).

Detailed explanation-5: -Nitrification, a process carried out by nitrifying bacteria, transforms soil ammonia into nitrates (NO3−), which plants can incorporate into their own tissues.