Nutrient cycles

• What are the two main cycles that recycle nutrients in natural ecosystems?

  Nitrogen cycle and phosphorus cycle
• What is the role of saprobionts in the nitrogen cycle?

  Break down organic matter to ammonia
• Why is ammonification important in the nitrogen cycle?

  It converts organic matter into ammonia for further processing
• What enzyme is used to break down proteins into amino acids during ammonification?

  Extracellular protease
• What enzyme is used to remove amino groups during ammonification?

  Deaminase
• What is the role of nitrifying bacteria in the nitrogen cycle?

  Convert ammonia to nitrate ions
• What is the intermediate product in the nitrification process?

  Nitrite ion (NO2-)
• Why is denitrification considered a wasteful process in the nitrogen cycle?

  It converts nitrate ions into nitrogen gas, which is lost to the atmosphere
• What can prevent denitrification from occurring?

  Well-drained and aerated soil
• What is the role of nitrogen-fixing bacteria in the nitrogen cycle?

  Convert nitrogen gas into ammonia
• Why is the relationship between nitrogen-fixing bacteria and leguminous plants considered mutualistic?

  Both organisms benefit from the relationship
• What form of phosphorus do plants take up from the soil?

  Phosphate ions (PO43-)
• How is phosphate released into the soil in the phosphorus cycle?

  Weathering of sedimentary rocks and decay of organic matter
• What is the role of mycorrhizae in plant nutrient uptake?

  Increase surface area and facilitate water and mineral uptake
• What is the primary benefit of mycorrhizae to plants?

  Better resistance to drought and easier uptake of inorganic ions
• Why are natural and artificial fertilizers used in agriculture?

  To replace nitrates and phosphates lost by harvesting and livestock removal
• What is a major environmental impact of nitrogen fertilizers?

  Reduction in biodiversity, leaching, and eutrophication
• What is leaching in the context of nitrogen fertilizers?

  Mineral ions dissolve in rainwater and are carried to rivers and lakes
• What is the process of eutrophication?

  Excess nitrate ions cause rapid algae growth, blocking light and depleting oxygen
• What is the final outcome of eutrophication in a waterway?

  Death of the ecosystem due to oxygen depletion
• What are the four stages of the nitrogen cycle?

  1. Ammonification: Organic matter broken down to ammonia
  2. Nitrification: Ammonia converted to nitrate ions
  3. Denitrification: Nitrate ions converted to nitrogen gas
  4. Nitrogen fixation: Nitrogen gas fixed into ammonia
• What are the environmental impacts of nitrogen fertilizers?

  • Reduction in biodiversity
  • Leaching of nitrates into waterways
  • Eutrophication leading to ecosystem death
• What is the role of mycorrhizae in plant health?

  • Increase surface area for water and mineral uptake
  • Act as a sponge to hold water and minerals
  • Help plants resist drought and take up inorganic ions more easily
• What are the key processes in the phosphorus cycle?

  • Weathering of sedimentary rocks releases phosphate
  • Decay of bones, shells, and bird excreta releases phosphate
  • Plants take up phosphate ions from the soil
• What are the benefits and drawbacks of nitrogen fertilizers?

  Benefits:

  • Increase crop yields
  • Help meet demands of growing population

  
  

  Drawbacks:

  • Reduce biodiversity
  • Cause leaching and eutrophication
• What is the relationship between nitrogen-fixing bacteria and leguminous plants?

  • Mutualistic relationship
  • Bacteria fix nitrogen gas into ammonia
  • Plants provide bacteria with nutrients and a habitat
• What are the steps involved in ammonification?

  1. Proteins broken down into amino acids by extracellular protease
  2. Amino acids broken down further to remove amino groups by deaminase
  3. Saprobionts use decomposition products for respiration
• What are the steps involved in nitrification?

  1. Ammonia converted to nitrite ions by nitrifying bacteria
  2. Nitrite ions converted to nitrate ions by nitrifying bacteria
• What are the steps involved in denitrification?

  1. Nitrate ions converted to nitrogen gas by denitrifying bacteria
  2. Process can be prevented by well-drained and aerated soil
• What are the steps involved in nitrogen fixation?

  1. Nitrogen gas reduced to ammonia by nitrogen-fixing bacteria
  2. Ammonia dissolves to form ammonium ions
  3. Bacteria live in root nodules of leguminous plants
• What are the key processes in the phosphorus cycle?

  • Weathering of sedimentary rocks releases phosphate
  • Decay of bones, shells, and bird excreta releases phosphate
  • Plants take up phosphate ions from the soil
• What are the environmental impacts of nitrogen fertilizers?

  • Reduction in biodiversity
  • Leaching of nitrates into waterways
  • Eutrophication leading to ecosystem death
• What is the role of mycorrhizae in plant health?

  • Increase surface area for water and mineral uptake
  • Act as a sponge to hold water and minerals
  • Help plants resist drought and take up inorganic ions more easily
• What are the benefits and drawbacks of nitrogen fertilizers?

  Benefits:

  • Increase crop yields
  • Help meet demands of growing population

  
  

  Drawbacks:

  • Reduce biodiversity
  • Cause leaching and eutrophication
• What is the relationship between nitrogen-fixing bacteria and leguminous plants?

  • Mutualistic relationship
  • Bacteria fix nitrogen gas into ammonia
  • Plants provide bacteria with nutrients and a habitat
• What are the steps involved in ammonification?

  1. Proteins broken down into amino acids by extracellular protease
  2. Amino acids broken down further to remove amino groups by deaminase
  3. Saprobionts use decomposition products for respiration
• What are the steps involved in nitrification?

  1. Ammonia converted to nitrite ions by nitrifying bacteria
  2. Nitrite ions converted to nitrate ions by nitrifying bacteria
• What are the steps involved in denitrification?

  1. Nitrate ions converted to nitrogen gas by denitrifying bacteria
  2. Process can be prevented by well-drained and aerated soil
• What are the steps involved in nitrogen fixation?

  1. Nitrogen gas reduced to ammonia by nitrogen-fixing bacteria
  2. Ammonia dissolves to form ammonium ions
  3. Bacteria live in root nodules of leguminous plants
• What are the key processes in the phosphorus cycle?

  • Weathering of sedimentary rocks releases phosphate
  • Decay of bones, shells, and bird excreta releases phosphate
  • Plants take up phosphate ions from the soil