Nitrogen cycle

• What is constantly being recycled like carbon and water?

  Nitrogen
• Why can't nitrogen in the atmosphere be used directly by plants or animals?

  It is very unreactive
• What percentage of the atmosphere is nitrogen gas (N₂)?

  78%
• Why is nitrogen needed for living organisms?

  For making proteins for growth
• What must nitrogen in the air be turned into for plants to use it?

  Mineral ions
• How do plants absorb mineral ions from the soil?

  By absorbing them from the soil
• How is nitrogen passed along food chains?

  In the form of proteins
• What do decomposers break down in the soil?

  Proteins in rotting plants and animals
• What do decomposers return to the soil?

  Nitrogen
• What is nitrogen fixation?

  The process of turning N₂ into mineral ions
• What are the two main ways nitrogen fixation occurs?

  Lightning and nitrogen-fixing bacteria
• How does lightning contribute to nitrogen fixation?

  It provides energy to convert N₂
• Where do nitrogen-fixing bacteria live?

  In roots and soil
• What are the four types of bacteria involved in the nitrogen cycle?

  Decomposers, nitrogen-fixing, nitrifying, and denitrifying bacteria
• What do decomposers do to proteins?

  They break them down into ammonia
• What do nitrifying bacteria convert ammonia into?

  Nitrites and nitrates
• What do denitrifying bacteria do in the nitrogen cycle?

  They convert nitrates back into N₂
• What is the final product of the nitrogen cycle?

  Nitrogen gas (N₂)
• How do different species of nitrogen-fixing bacteria contribute to the nitrogen cycle?

  They produce different forms of nitrogen compounds
• How do nitrogen-fixing bacteria and decomposers work together in the nitrogen cycle?

  They convert nitrogen into usable forms for plants
• What is the role of ammonium in the nitrogen cycle?

  It is a form of nitrogen plants can use
• What do plants use nitrogen for?

  To make proteins
• How does nitrogen fixation benefit plants?

  It provides them with essential nutrients
• How does the nitrogen cycle illustrate the interdependence of organisms?

  Organisms rely on each other for nitrogen
• What happens to nitrogen in decaying matter?

  It is returned to the soil
• What is the significance of the nitrogen cycle in ecosystems?

  It recycles nitrogen for living organisms
• How do human activities impact the nitrogen cycle?

  They can disrupt natural nitrogen processes
• What are the consequences of excess nitrogen in ecosystems?

  It can lead to pollution and eutrophication
• What can plants use for nitrogen?

  Nitrogen-fixing bacteria
• What do nitrogen-fixing bacteria do to decaying matter?

  They turn it into nitrates and nitrites
• What are different species of nitrogen-fixing bacteria responsible for?

  Producing nitrates and nitrites
• How do nitrogen-fixing bacteria convert atmospheric nitrogen?

  They turn it into ammonia
• What happens to nitrates in the soil after denitrifying bacteria act on them?

  They are converted back into nitrogen gas
• Where are denitrifying bacteria often found?

  Waterlogged soils
• Where do some nitrogen-fixing bacteria live?

  In the soil
• Where do other nitrogen-fixing bacteria live?

  In nodules on legume plant roots
• What happens to nitrogen stored in plants when they decompose?

  It is returned to the soil
• What can nitrogen-containing ions do during plant growth?

  They can leak out of nodules
• What relationship do plants have with bacteria?

  Symbiotic relationship
• What do bacteria gain from their relationship with plants?

  Food from plant sugars