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Nitrogen Cycle
What is the Nitrogen Cycle?
Why do we need nitrogen? ______ living organisms need nitrogen in order to _______
proteins and __________ _____. Most _______ get the nitrogen they need by _________
__________.
Nitrogen must be _________ with something else in order for it to be used. Most organisms
can ______ use the nitrogen in the air. Nitrogen must be _________. It needs to be
__________ with other elements.
The Nitrogen Cycle: The process by which _________is removed from the atmosphere,
______ in the soil by ___________, incorporated in other living things, and then _________
back into the atmosphere.
Nitrogen _________: The process of ___________ free nitrogen gas (from the air) into a
________ form of nitrogen. Performed by _________
____________: Some of these bacteria live in bumps called ________ on the _______ of
certain plants.
What kind of plants? Bacteria live in the _______ of plants called __________. Examples:
Mutualism: ______ species benefit. The _________ feed on plant’s _______. The
________ is supplied with ________ in the useable form.
Farmers will often _______ alfalfa in their fields so that their ______ will be rich in
________. _________ in the roots “fix” the nitrogen so it can be used.
Now what? Once _________ in the roots of plants have _________ the nitrogen, the
_________ can be used by organisms to _______ proteins and other complex substances.
Plans absorb the _________. Animals eat the ___________.
Recycling: __________ break down these complex compounds in __________ _________
and in the bodies of dead organisms. _______ is now __________ to the soil. Nitrogen can be
__________over and over again. _______________ can also return ________ nitrogen back
to the _____.
Human Influence:
Question: Nitrogen Fertilizer is often added to sols to increase the growth of crops. Which of
these ecosystems would most likely be harmed by the use of nitrogen fertilizers?
Answer:_________________