Zusammenfassung der Ressource
The nitrogen cycle
- Nitrogen fixation
- Mutualistic nitrogen fixing bacteria, otherwise known as bacteria in root
nodules (legumes, peas, beans, lentils and clover) reduce gaseous nitrogen
to ammonia, similarly to the free living nitrogen fixing bacteria.
- The bacteria synthesises the nitrogen into amino acids, and
the plant utilieses this. It is mutualistic as both the plant and
the bacteria benefit from this. The bacteria recieves
carbohydrates.
- Free living nitrogen fixing bacteria, otherwise
known as bacteria in the soil, reduce gaseous
nitrogen to ammonia.
- Bacteria use ammonia to synthesise amino acids and internalise
them.
- The bacteria then dies, and decays, releasing the
nitrogen compounds into the soil.
- Ammonification/decomposition
- Plants absorb nitrates from the soil, which are used to
form amino acids (proteins).
- Plants are eaten - therefore the amino
acids are absorbed and assimilated into
animals amino acids.
- Assimilation - The absorption of nutrients into the
body after digestion in the intestine and its
transformation in biological tissues and fluids.
- Both the plant (producer) and animal (consumer) die. Dead
matter/detritus still contain nitrogen still fixed in organic
molecules.
- Decomposers release ammonia into the soil
- Nitrification
- Nitrifying bacteria oxidise ammonia to nitrites.
- Different nitrifying bacteria oxidise nitrites to nitrates.
- Plants absorb nitrates from the soil.
- Denitrification
- Reduces nitrates to nitrogen gas, replenishing the atmosphere.
- Problems in waterlogged soil and aquatic conditions,
as the sediment is in anaerobic conditions. The
anaerobic basterica reduces nitrates and ammonium
back to nitrogen using nitrates as oxygen.