Introduction to Ecology: Nitrogen Cycle
Nitrogen is an element that is part of proteins and nucleic acids. Like some other substance, nitrogen is
recycled in the environment. Plants, animals, and bacteria are all important to the nitrogen cycle.
A. Complete the paragraph below.
In the nitrogen cycle, atmospheric nitrogen is converted into usable nitrogen compounds. Certain (1)
____________________ live in the nodules on the roots of (2) ____________________. These bacteria
take in atmospheric nitrogen and convert it to (3) ____________________ that the legumes can use. This
process is known as (4) ____________________. Animals such as omnivores and (5)
____________________ eat these plants, thus consuming nitrates that their bodies can use. When the
legumes die and when animals die or excrete (6) ________________, bacteria in the (7)
____________________ convert nitrogen compounds in the wastes to ammonia. This process is called (8)
____________________. Since plants cannot use ammonia, other bacteria convert ammonia to nitrates.
This two-step process is called (9) ______________. Finally, other bacteria convert the nitrates into
atmospheric nitrogen by a process called
(10) ____________________.
B.
Study the diagram of the nitrogen cycle below. Write the name of each process in the appropriate blank.