The Nitrogen Cycle
Picture Source: Sandner, L (2009). Investigating Science 9. Pearson.
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_______________________________: This cycle shows how nitrogen atoms are reused/recycled through
biotic and abiotic parts in the environment.
_______________________ causes nitrogen gas (N2) to react with oxygen in the air to produce
________________________ (NH3). _________________________ changes the ammonia into
__________________ and then into ______________________ (NO3) - this process is known as
_____________________________________________________.
Some bacteria (____________________________________) in the soil and also in nodules on the roots of
certain plants, can also change nitrogen in the air into ammonia and then nitrifying bacteria changes the
ammonia into nitrites and then into nitrates (NO3) - which can be used by ________________________
Nitrates _____________________________ in rainwater, enter the soil and are ______________________
by plant roots. Plant cells use nitrates to make _________ (genetic material) and to make _______________.
Plants are _______________________ by animals. Animals break down plant proteins into
________________________ and then use amino acids to make animal ________________________.
a)b) When plants or animals die, ______________________________ (including bacteria) break down
nitrogen containing chemicals into simpler chemicals like ___________________ (NH3).
c) Feces and urine of animals also have nitrogen containing chemicals that decomposers break down
into ammonia.
Some bacteria can change nitrites into nitrates which can then be used by plants again (step 3) or step 7
occurs.
Some bacteria (________________________________) can change nitrates into nitrites and then into
nitrogen gas (N2) and in this way return nitrogen to the _________________________________.
The process occurring in step 7 is known as __________________________________.
These steps are continuously repeated. In this way nitrogen atoms are continuously reused/recycled in an
ecosystem.