AP BIOLOGY

Detailed explanation-1: -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-2: -The nitrogen cycle is largely dependent on microbial processes. Bacteria fix nitrogen from the atmosphere in the form of ammonia (NH3) and convert the ammonia to nitrate (NO3-). Ammonia and nitrate are absorbed by plants through their roots.

Detailed explanation-3: -The bacteria get energy through photosynthesis and, in return, they fix nitrogen into a form the plant needs. The fixed nitrogen is then carried to other parts of the plant and is used to form plant tissues, so the plant can grow.

Detailed explanation-4: -The Rhizobium or Bradyrhizobium bacteria colonize the host plant’s root system and cause the roots to form nodules to house the bacteria (Figure 4). The bacteria then begin to fix the nitrogen required by the plant.

Detailed explanation-5: -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.