The Nitrogen Cycle

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The Nitrogen Cycle
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Nitrogen Cycle Nitrogen Cycle Nitrogen Cycle

N2
atmosphere
lightning fixed Fertilizer Factory Fertilizer Factory
Denitrifying bacteria Denitrifying bacteria
Nitrates
Plants Bacteria
Decay Waste
Animals Ammonia
Decomposers

Bacteria in Nodules
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Nitrogen Facts

• Nitrogen is necessary for life
• Essential for proteins and DNA
• Circulates through biotic and abiotic systems
• Found in fertilizer with potassium and phosphorus
• Plants use nitrogen for growth.
• Earths atmosphere is 80 nitrogen gas (N2).
• Nitrogen gas is a form that very few organisms
  can use (they cant absorb it directly).
• In order to be used by organisms, nitrogen gas
  must be fixed

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3 Steps of the Nitrogen Cycle

• Nitrogen Fixation
• Conversion of nitrogen gas in the atmosphere to
  ammonia (NH4) by adding oxygen is done by
  nnitrogen fixing bacteria (rhizobia) use special
  enzymes to fix nitrogen (react the nitrogen with
  oxygen or hydrogen).
• Lightning provides enough energy to "burn" the
  nitrogen and fix it in the form of nitrate, NO3-
  by adding oxygen (this process is duplicated in
  fertilizer factories to produce nitrogen
  fertilizers).

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Nitrogen Cycle continued

• Nitrification
• -conversion of ammonia to nitrates (chemicals of
  nitrogen and oxygen)
• -done by nitrifying bacteria

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Nitrogen Cycle continued

• Denitrification
• -conversion of nitrates to nitrogen gas
• -done by denitrifying bacteria

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• The Nitrogen Cycle Explained
• Fixed nitrogen can be absorbed by plants as
  ammonium (NH4), or it can be converted into
  nitrate (NO3-) by nitrifying bacteria.
• Most plants can take up nitrates and convert it
  to amino acids and then possibly proteins.
• 3. Animals acquire all of their amino acids when
  they eat plants (or other animals).
• 4. When plants or animals die (or release waste)
  the nitrogen is returned to the soil.

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• 5. The nitrogen that is usually returned to the
  soil in animal wastes or in the output of the
  decomposers, is ammonia (NH3). Ammonia is rather
  toxic.
• 6. Nitrifying bacteria in soil or water convert
  ammonia (NH4) to nitrates (NO3-), which are
  taken up by plants to continue the cycle.
• 7. The final step to complete the nitrogen cycle
  is completed by denitrifying bacteria which
  convert nitrates (NO3-) back into atmospheric
  nitrogen gas (N2) in order to return it to the
  air.

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Ecosystem can experience nitrogen overload

• This can happen by...
• 1. adding fertilizer
• -increases plant growth
• 2. growing larger crops
• 3. burning fossil fuels
• -releases nitrogen-containing chemicals into air
  that re-enter cycle

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Effects of Nitrogen Overload

• 1. Soils-nitrogen saturation occurs, leading to
  run-off water pollution this damages roots and
  stunts growth, and increases soil acidity, which
  kills soil organisms.
• 2. Atmosphere-nitric acid falls to Earth as acid
  rain, which kills fish, birds, amphibians, and
  trees.
• 3. Fresh Water-increase in nitrates increases
  algae weeds and we get eutrophication (build up
  of nutrients) this harms drinking water, and
  reduces human bodys ability to carry oxygen to
  cells (anaemia)

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• 4. Marine Ecosystems -algal blooms cause a Red
  Tide, oxygen gets used up and reduces life.
• 5. Biodiversity-as extreme conditions
  (temperature, acidity, precipitation) increase,
  biodiversity decreases