AP BIOLOGY

Detailed explanation-1: -Through lightning: Lightning converts atmospheric nitrogen into ammonia and nitrate (NO3) that enter soil with rainfall. Industrially: People have learned how to convert nitrogen gas to ammonia (NH3-) and nitrogen-rich fertilisers to supplement the amount of nitrogen fixed naturally.

Detailed explanation-2: -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.

Detailed explanation-3: -Plants get the nitrogen that they need from the soil, where it has already been fixed by bacteria and archaea. Bacteria and archaea in the soil and in the roots of some plants have the ability to convert molecular nitrogen from the air (N2) to ammonia (NH3), thereby breaking the tough triple bond of molecular nitrogen.

Detailed explanation-4: -Nitrogen returns to the soil when organisms release waste or die and are decomposed by bacteria and fungi. Nitrogen is released back to the atmosphere by bacteria get their energy by breaking down nitrate and nitrite into nitrogen gas (also called denitrification).