AP BIOLOGY

Detailed explanation-1: -Some of the nitrogen-fixing bacteria convert atmospheric nitrogen into ammonia making it available to plants.

Detailed explanation-2: -Nitrogen fixation is carried out naturally in soil by microorganisms termed diazotrophs that include bacteria, such as Azotobacter, and archaea. Some nitrogen-fixing bacteria have symbiotic relationships with plant groups, especially legumes.

Detailed explanation-3: -Atmospheric fixation occurs when the high temperature of lightning splits the nitrogen gas so it bonds with oxygen and moisture in the air to form nitrates that fall to the earth with rain. This natural fertilization benefits plants.

Detailed explanation-4: -Nitrogen makes up 78 per cent of the air we breathe, and it’s thought that most of it was initially trapped in the chunks of primordial rubble that formed the Earth. When they smashed together, they coalesced and their nitrogen content has been seeping out along the molten cracks in the planet’s crust ever since.

Detailed explanation-5: -Nitrogen is fixed, or combined, in nature as nitric oxide by lightning and ultraviolet rays, but more significant amounts of nitrogen are fixed as ammonia, nitrites, and nitrates by soil microorganisms. More than 90 percent of all nitrogen fixation is effected by them.