Nitrogen Cycle

• What percentage of gas in the atmosphere is nitrogen?


  78%
• Why can't nitrogen be used directly by plants or animals?

  Because it is very unreactive
• What is nitrogen needed for?

  Making proteins for growth
• Where do plants get their nitrogen from?


  Soil
• Where do animals get protein from?

  Eating plants
• Nitrogen fixation


  it's the process of turning N2 , from the air into nitrogen compounds in the soil which plants can use. There are two main ways that this happens
• How many ways can nitrogen be turned in to nitrogen compounds?

  2
• What are the ways that turn nitrogen into nitrogen compounds?


  - Lightning

  - Nitrogen-fixing bacteria
• Nitrogen-fixing bacteria


  Is in soil and the roots of some plants
• Lightning


  There's so much energy in a bolt of lightning that it's enough to make nitrogen react with oxygen in the air to give nitrates.
• How many types of nitrogen-foxing bacteria are there?

  4
• What are the types of nitrogen-fixing bacteria?


  - Decomposers

  - Nitrifying bacteria

  - Nitrogen-fixing bacteria

  - Denitrifying bacteria
• Decomposers


  - Break down proteins (in rotting plants and animals) and urea (in animal waste) and turn them into ammonia (a nitrogen compound)

  - This forms ammonium ions in the soil
• Nitrifying bacteria


  - Turn ammonium ions in decaying matter into nitrates (nitrification)
• What is nitrogen-fixing bacteria?


  Turn atmospheric N, into nitrogen compounds that plants can use
• Denitrifying bacteria


  - Turn nitrates back into N, gas.

  - This is of no benefit to living organisms