Transcript The Nitrogen Cycle

The Nitrogen Cycle
By: Caitlin, Jade, Connor, and
Brandon M.
Nitrogen Fixation
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The process of combining
nitrogen gas with hydrogen
to form ammonia.
Only happens in absence of
oxygen.
Even the tiniest bit of
oxygen could ruin the entire
process.
Nitrogen fixing bacteria live
in the soil within capsules
that admit no oxygen.
Step 1:Assimilation
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The nitrogen-fixing bacteria
produces ammonia that
spreads through the soil.
The plants absorb it to make
proteins, nucleic acids, and
other nitrogen-containing
molecules.
Animals eat the plants and
build their own molecules.
Nitrogen assimilation is
absorbing and incorporating
nitrogen into plant and
animal compounds.
Step 2:Ammonification
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Animals get rid of excess nitrogen through their waste which a
soil bacterium turns back into ammonia.
Bacteria also converts nitrogen in dead tissues to ammonia.
The ammonia is reabsorbed by plants, and it starts all over
again.
Ammonification is bacteria producing ammonia during the
decay of nitrogen containing organic matter.
Step 3:Nitrification
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The ammonia that is not absorbed by plants is turned
into nitrate by bacteria.
Nitrate can also be absorbed by plants.
Nitrification is the production of nitrate from
ammonia.
Step 4:Denitrification
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Another kind of bacterium turned the rest of
the nitrate into nitrogen gas.
The nitrogen gas is released into the
atmosphere which completes the nitrogen
cycle.
Denitrification is the conversion of nitrate to
nitrogen gas.
Other Facts..
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Atmosphere is 79% nitrogen gas.
Nitrogen atoms are connected by a really
strong triple covalent bond.
Bacteria could fix nitrogen before
photosynthesis introduced oxygen.
The population of plants in the ecosystem
counts on how much nitrate and ammonia is in
the soil.
That is why farmers use fertilizer.
Our Role
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Humans do many things to alter the nitrogen
cycle.
We contaminate the groundwater with nitrate
from the fertilizers.
We are releasing solid forms of nitrogen by
fossil fuel combustion and forest burning.
Sewage wastes are releasing ammonia.
Resources
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Our Biology book.
http://www.physicalgeography.net/fundamenta
ls/9s.html
Questions
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What Percent of the Atmosphere is nitrogen
gas?
A) 98%
B) 79%
C) 26%
D) 71%
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Which gas must be absent for nitrogen-fixation
to occur?
A) Nitrogen
B) Hydrogen
C) Ammonia
D) Oxygen
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What does not convert to ammonia?
A) Rocks
B) Dead Animals
C) Dead Plants
D) Animal Wastes
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Where does the nitrogen-fixing bacteria
typically start out?
A) Soil
B) Plants
C) Animals
D) Atmosphere
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What converts one chemical into another
chemical more than once in the nitrogen cycle?
A) Animals
B) Bacteria
C) Plants
D) Humans
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What happens first in the nitrogen cycle?
A) Assimilation
B) Nitrogen-fixation
C) Ammonification
D) Denitrification
True or False
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Too little of nitrogen can limit plant growth in
a certain area.
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Humans do not affect the nitrogen cycle.