Nitrogen Cycle

• Nitrogen is 78% of atmosphere
• Organisms need nitrogen to build proteins
• Nitrogen is passed through food webs
• Plants obtain nitrogen from soil, animals from food
• Living organisms have to trap nitrogen
• Organisms do not use nitrogen as a gas (N2), but in the form of nitrates (NO) or ammonium (NH4)
• Nitrates : A form of nitrogen that can be used by plants to make proteins
• Ammonia : Gas containing nitrogen that is converted into nitrites and nitrates by bacteria in the nitrogen cycle
• Nitrites : Form of nitrogen that is converted into nitrites by bacteria
• Main ways of converting nitrogen into nitrates:

  • Industrial process
  • lightning
  • Fixation by legumes (Plants - peas and beans)
• Industrial process : Artificial fertilizers are made.
• Lightning : Provides enough energy for small amounts of nitrogen to become nitrates
• Fixation by legumes :

  • Most efficient
  • Bacteria makes swelling in legumes.
• Steps in nitrogen cycle:

  1. Nitrogen fixing bacteria and lightning changes nitrogen gas into nitrates.
  2. Nitrates dissolve in water, in soil and plants absorb it. Using it to make proteins
  3. Plant protein consumed by animals to make animal protein.
  4. Consumers release nitrogen from urine and faeces.
  5. Decomposers obtain nitrogen from bodies, and breakdown of urine and faeces, forming ammonia.
  6. Bacteria converts ammonia into nitrates.
  7. Detrifying bacteria release nitrogen back into the atmosphere, and break down nitrates to form nitrogen gas. Fires release nitrogen