The Nitrogen Cycle
What is the Nitrogen Cycle?
• Nitrogen Cycle – a
natural cyclic process
in the course of which
atmospheric nitrogen
enters the soil and
becomes part of living
organisms, before
returning to the
atmosphere.
What is Nitrogen?
• Nitrogen is a
colorless,
odorless,
tasteless,
nontoxic gas.
What is Nitrogen?
• Nitrogen, an essential part of the
amino acids, is a basic element of life.
What is Nitrogen?
• Makes up 78 percent of the Earth’s atmosphere.
How does the Nitrogen Cycle work?
• Atmospheric
Nitrogen is
carried to the
earth by
Precipitation.
How does the Nitrogen Cycle work?
• Bacteria in the soil convert the
atmospheric Nitrogen gas (N2), into
nitrates (NO3) and ammonium ions (NH4)
which can then be used by plants and
fungi.
• This process is called:
Nitrogen Fixation
How does the Nitrogen Cycle work?
• The nitrogen
then passes
through the
food chain
from plants to
herbivores to
carnivores.
How does the Nitrogen Cycle work?
• Animals poop …………………
How does the Nitrogen Cycle work?
• ………..and pee.
• Animal wastes
have high
Nitrogen levels.
How does the Nitrogen Cycle work?
• This nitrogen
gets returned
to the soil for
decomposition
by bacteria and
re-use.
How does the Nitrogen Cycle work?
SUMMARY
• All organisms produce wastes and
eventually die.
• When an organism dies its proteins are
slowly broken down into ammonia
compounds, then to nitrites, and finally
back to nitrates.
• The nitrates can then reenter the cycle.
How does the Nitrogen Cycle work?
SUMMARY
• At various stages in the decay process,
denitrifying bacteria [soil bacteria that
reduce nitrates (NO3)or nitrites (NO2)to
gaseous nitrogen and some nitrous oxide]
can break down nitrites and nitrates,
releasing nitrogen gas back into the
atmosphere.
Assignment
1. Draw a diagram of the Nitrogen cycle
that follows these notes.
2. Write an essay that explains how the
nitrogen cycle works and what would
happen if any link in the cycle were
removed. You should be able to
describe in great detail with specific
examples.