NITROGEN CYCLE
FLT: I will understand that nitrogen is continually recycled between
living and nonliving things by bacteria by completing the Nitrogen
Cycle diagram.
Introduction:
Nitrogen is an important part of all living organisms. Nitrogen gas
makes up a big portion of the atmosphere and the air that organisms
breathe. Unfortunately, nitrogen gas cannot be used in its natural form
directly by most living organisms. It must be converted into another
form in order for living organisms to use it.
To do: On the line at the top write the title: The Nitrogen Cycle.
To do: In the
write “ATMOSPHERE” - middle top
To do: In the
write “SOIL” – bottom left
A. Nitrogen Gas
To do: In the
write the words “NITROGEN GAS”
To do: In the
write:
“Nitrogen gas cannot be used directly by plants or animals”
B. Converting Nitrogen
To do: In the
write:
“Nitrogen must be converted to a usable form”
C. Plants with bacteria
Certain plants, called legumes (example: soybeans), have bacteria on
their roots that can convert nitrogen into a usable form.
To do: In the box with plants write:
“Roots of legumes contain bacteria”
D. Nitrogen-fixing bacteria
Nitrogen-fixing bacteria can convert nitrogen gas into ammonia.
Ammonia can then get converted into a form that plants and animals can
use. Essentially they “FIX” the nitrogen so it can be used! 
To do: In the
write:
“Nitrogen-fixing bacteria”
To do: Fill-in the box with what the nitrogen-fixing bacteria do.
E. Nitrifying bacteria
Once nitrogen-fixing bacteria convert nitrogen gas into ammonia,
another type of bacteria in the soil, nitrifying bacteria, convert the
ammonia into nitrates and nitrites. Plants can then take the nitrates and
nitrites into their roots so the nitrogen can be used by the plant.
Animals will then eat the plants to get the nitrogen that they need for
their tissues.
To do: In the
write:
“Nitrifying bacteria”
To do: Fill-in the box with what the nitrifying bacteria do.
F. Decomposers
When plants and animals die, their body parts need to get recycled. The
nitrogen in their tissues is recycled back to the soil by decomposers.
Another thing that is recycled is animal excrement (aka poop!).
Decomposers, such as worms, fungi and bacteria, “decompose” the tissue
and return the nitrogen, in the form of ammonia, back to the soil.
To do: In the
write:
“Decomposers”
To do: Fill-in the box with what decomposers do.
G. Denitrifying bacteria
Eventually any excess nitrates and nitrites that are in the soil will need to
be returned to the atmosphere. There is another type of bacteria, called
denitrifying bacteria, that convert nitrates and nitrites back into
nitrogen gas. The nitrogen gas is returned to the atmosphere to start the
cycle all over again. As a helpful hint, “de-” means to “undo”. So the
“denitrifying bacteria” are “undoing” the nitrogen to return it to its
original form.
To do: In the
write:
“Denitrifying bacteria”
To do: Fill-in the box with what denitrifying bacteria do.
H. Ocean
Everything that is occurring on land is also occurring in the ocean. There
are bacteria in the ocean that can convert nitrogen in the water into a
usable form. There are also organisms that breakdown dead marine
organisms and return the nitrogen to the earth. There are also organisms
that return nitrogen from ocean floor to the water.
To do: In the bottom right hand corner draw a box
To do: Write in the box: “All of this occurs in the ocean, too”
I. Complete the chart
To do: In the
write:
“Nitrogen gas is returned to the atmosphere”
To do: Color the soil and atmosphere appropriate colors.
To do: Work on the next activity.