Nitrogen Cycle - LC Biology

Step 1

• Nitrogen in atmosphere in the form of nitrogen gas. Must be converted to nitrates before it can be used by plants

• This happens by bacteria and lightning and artificially by the Faber Process

Step 2

• Nitrates enter soil in rain and are absorbed through plant roots - used to create plant proteins

• Some proteins then assimilated by animals when plants eaten by animals

• Some nitrogen lost from animals during excretion

• When plants and animals die, they are decomposed by bacteria and fungi and nitrogen in their bodies is turned to ammonia

Step 3

• Ammonia is converted to nitrites by bacterial action (nitrification) but nitrites are toxic to plants

• Nitrites are converted to nitrates (also nitrification)

• Bacteria that cause this change = nitrifying bacteria

Step 4

In the soil, bacteria break down nitrates releasing nitrogen back (dentrification) - cycle completed