Nitrogen Cycle Notes | Ms. Laura Branch

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 not __________ 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:_________________

© Laura Branch 2017