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The Carbon and Nitrogen
Cycles
What is Carbon?
Carbon is an
element that
is in all living
things.
 Molecules
containing
carbon are
called Organic.

Carbon Cycle
 The
movement of carbon
from the environment into
living things and then back
again is the Carbon Cycle.
 You already know how
carbon dioxide cycles
between photosynthesis and
cellular respiration.
Carbon Cycle
Carbon dioxide in the air enters
into living things through
photosynthesis.
 Oxygen and glucose produced
from photosynthesis are then used
by plants and animals for cellular
respiration.
 Cellular respiration produces
carbon dioxide to be released
again.

Carbon Cycle

Keep in mind all living things have
carbon in them, so when they die,
decomposers help return that
carbon to the environment and soil.
Carbon Cycle
Carbon in the environment is
used to make coal, oil, and
natural gas (fossil fuels).
 Fossil fuels are burned in a
process called Combustion.
 Combustion releases carbon
dioxide back into the air.

What is nitrogen?
o
Nitrogen is
used to build
proteins and
DNA.
Nitrogen Cycle
The movement of nitrogen from
the environment to living things
and back again is the Nitrogen
Cycle.
 About 78% of the Earth’s
atmosphere is nitrogen gas,
however most organisms cannot
use nitrogen when it’s in a gas
form.

Nitrogen Cycle

Nitrogen fixation
is when lightning
or bacteria in
the soil change
nitrogen gas into
a form that can
be taken up by
plant roots.
Nitrogen Cycle
Animals eat the plants and
therefore take in nitrogen.
 When animals and plants die,
decomposers help return the
nitrogen to the soil.
 Other bacteria then change the
nitrogen in the soil back into a
gas to be released back into the
air.
