Transcript What is Nitrogen?

The
Nitrogen Cycle
Chapter 16.3
The largest single source of nitrogen is in the
atmosphere.
Nitrogen makes up 78% of our air!
What is the nitrogen cycle?
Nitrogen from the atmosphere gets fixed,
used by plants and animals, and later returned
to the atmosphere.
It is one of nature’s
great ironies…
Nitrogen is an essential
component of
DNA, RNA, and Proteins.
Most living organisms are
unable to use nitrogen as it
exists in the atmosphere!
Simple Nitrogen Cycle Animation
• http://www.classzone.com/books/ml_scienc
e_share/vis_sim/em05_pg20_nitrogen/em05
_pg20_nitrogen.html
End Show
What happens to
atmospheric nitrogen
(N2) in the nitrogen
cycle?
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Atmospheric nitrogen is converted
to ammonia or nitrates.
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Atmospheric
Nitrogen (N2)
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Ammonia (NH3)
Nitrogen combines
with Hydrogen
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Nitrates (NO3)
Nitrogen combines
with Oxygen
How does
atmospheric
nitrogen get
changed into a
usable form?
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Nitrogen in
the air
nitrogen fixing plant
eg pea, clover
animal protein
plant made
protein
root nodules
(containing nitrogen
fixing bacteria)
denitrifying
bacteria
nitrates absorbed
dead plants & animals
urine & feces
decomposition by bacteria & fungi
nitrates
bacteria
(nitrifying bacteria)
ammonia
nitrites
bacteria
Other ways that nitrogen
returns to the atmosphere…
Emissions from industrial combustion and
gasoline engines
Volcano eruptions
By traveling through one of the four
processes in the Nitrogen Cycle!
(1) Nitrogen Fixation
(4) Denitrification
Nitrogen
Cycle
(3) Nitrification
(2) Ammonification
There are three ways that
nitrogen gets “fixed”!
(a) Atmospheric Fixation
(b) Industrial Fixation
(c) Biological Fixation
Bacteria
Biological Fixation
“Nitrogen Fixing Bacteria”
Symbiotic Relationship
(“fixes” 70% of N2)
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What is
“nitrogen fixation”
and
what does it mean
nitrogen gets
“fixed”?
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“Nitrogen Fixation” the process that breaks strong
(3 covalent bonds) two-atom nitrogen molecules apart so
they can combine with oxygen or hydrogen.
Oxygen
Hydrogen
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Hydrogen
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Oxygen
Atmospheric Fixation
(5 to 8% of the Process)
Lightning “fixes” Nitrogen!
Lightning breaks nitrogen
molecules apart . Combines
with oxygen forming nitrogen
oxides (N2O).
N2O dissolves in rain, forming
nitrates.
Nitrates (NO3) are carried to
the ground with the rain.
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O Nitrogen
combines
with Oxygen
Nitrogen oxides forms
(N2O)
(NO3)
Nitrogen
oxides dissolve
in rain and
change to
nitrates
Plants use
nitrates to
grow!
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H3
Industrial Fixation
Industrial Plant combines
nitrogen and hydrogen
(NH3)
Ammonia is formed
Ammonia is used a fertilizer in soil
Symbiotic Relationship
Bacteria
Bacteria on the roots of
legume family plants
and provide the plants
with ammonia (NH3) in
exchange for the
plant’s carbon and a
protected home.
Legume plants
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NH3
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Roots with nodules
where bacteria live
Nitrogen changes into
ammonia.
Most atmospheric nitrogen
(N2) is “fixed” and changed to
ammonia (NH3). Ammonia is
highly toxic to many
organisms.
Can plants use
ammonia?
Very few plants can use
ammonia (NH3)…
(1) Nitrogen Fixation
(2) Ammonification
…but, fortunately the
second process
Ammonification can help!
What is
ammonification?
Ammonification: Bacteria decomposers break down
amino acids from dead animals and wastes into nitrogen
ammonium.
Why is
ammonification
necessary?
Plants cannot use the organic forms of nitrogen
which are a result of:
(1) wastes (manure and sewage)
(2) compost and decomposing roots and leaves
How does
ammonification
occur?
Bacteria converts organic nitrogen to
ammonium (NH4)
Bacteria
Ammonium (NH4) is used by
some plants
Ammonium (NH4) is
stored in soil.
What happens to
ammonium (NH4) stored
in the soil?
It travels through the
third process
of the nitrogen cycle called
Nitrification!
(1) Nitrogen Fixation
(3) Nitrification
(2) Ammonification
Nitrifying bacteria in soil
combine ammonia with oxygen
Ammonia changes to nitrites
Nitrifying bacteria in soil
convert nitrites to nitrates
Ammonia
Nitrites
Nitrates
(NH3)
(NO2)
(NO3)
Plants absorb nitrates
and grow!
How does
nitrogen reenter the
atmosphere
in the
nitrogen
cycle?
Through the fourth
process called
denitrification!
(4) Denitrification
(3) Ammonification
(1) Nitrogen Fixation
(2) Nitrification
What does
denitrification
do?
Denitrification converts nitrates (NO3) in the soil
to atmospheric nitrogen (N2) replenishing the
atmosphere.
Nitrates (NO3)
in Soil
How does the
denitrification
process work?
Nitrates in soil
Denitrifying bacteria live deep in soil and in aquatic
sediments where it is difficult for them to get oxygen.
They use nitrates instead of oxygen, leaving nitrogen
gas as a byproduct…completing the nitrogen cycle!
(N2)
(NO3)
(a)
(b)
N2
N2 O
(4) Denitrification
(1) Nitrogen Fixation
(c)
Nitrogen
Cycle
(3) Nitrification
(2) Ammonification
NO3
Ammonia is converted
to nitrites and nitrates.
NH3
Nitrates in Soil
Organic nitrogen is
converted to ammonium.