Transcript Nitrogen cycle FINAL

The Biogeochemical Cycles
Nitrogen Cycle
Biology I
Ecology
What is Nitrogen?
• Nitrogen - most abundant
element in the Earth’s
atmosphere.
• Nitrogen cannot be absorbed
directly by plants & animals
until it is converted into
compounds they can use.
Nitrogen Cycle Steps
• Step 1- Nitrogen Fixation- Special
bacteria convert nitrogen gas (N2) to
ammonia (NH3) which the plants
can use.
–Assimilation
• Step 2- Nitrification- Nitrification
is the process which converts
ammonia into material which the
plants can use as nutrients.
• Step 3- Ammonification- After
living organisms have used
nitrogen, decomposers convert the
nitrogen-rich waste compounds
into simpler ones .
• Step 4- Denitrification- Final step
in which other bacteria convert the
simple nitrogen compounds back
into nitrogen gas (N2), to be
released into the atmosphere
How do humans affects
the Nitrogen Cycle?
• Nitric Oxide (NO) is released into the atmosphere
when any type of fuel is burned. This includes
byproducts of internal combustion engines.
• Nitrous Oxide (N2O) is released into the
atmosphere through bacteria in livestock waste
and commercial fertilizers applied to the soil.
• Removing nitrogen from the Earth’s crust and soil
when we mine nitrogen-rich mineral deposits.
• Discharge of municipal sewage adds nitrogen
compounds to aquatic ecosystems which disrupts
the ecosystem and kills fish.
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 & faeces
decomposition by bacteria & fungi
nitrates
bacteria
(nitrifying bacteria)
ammonia
nitrites
bacteria
Nitrogen in
the air
nitrogen fixing plant
eg pea, clover
animal protein
plant made
protein
root nodules
(containing nitrogen
fixing bacteria)
dead rabbit
denitrifying
bacteria
nitrates absorbed
dead plants & animals
urine & faeces
decomposition by bacteria & fungi
nitrates
bacteria
ammonia
nitrites
(nitrifying bacteria)
bacteria