Circulation of nutrients

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Circulation of nutrients
2012-09-20 13:51:28

Advanced Higher Biology - Unit 2 - Circulation of nutrients
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  1. What is decompostition?
    Decomposition is the breakdown of organic matter with the release of inorganic nutrients into the surrounding soil
  2. What is the difference between detrivores and decomposeers? Explain this with reference to their role in decomposition and give examples of organisms
    Detrivores (eg worms) increase decomposition rate as they reduce the size of the detritus, making it easier for the decomposers (bacteria and fungi) to break down detritus to form humus
  3. "Decomposers respiration is the ultimate releaser of energy and carbon dioxide fixed in photosynthesis"  What is meant by this statement?
    Through the breakdown of the remains of dead animals and plants, decomposers release all the chemical energy stored as biomass back into the ecosystem
  4. What is the limiting factor in decomposition?
    Nitrogen availability
  5. Draw the nitrogen cycle
  6. What are the five main stages of the nitrogen cycle?
    • Nitrogen fixation
    • Ammonification
    • Nitrification
    • Assimilation
    • Denitrification
  7. What is nitrogen fixation?  What are the three ways nitrogen can be fixed?
    • Nitrogen fixation is when atmospheric nitrogen (N2) is converted into ammonia (NH3)
    • Non-natural processes eg haber process, lightning, fixation by bacteria
  8. What type of nitrogen fixing bacteria is found in legumes?
    Rhizobium sp
  9. What enzyme is a catalyst for nitrogen fixation?
  10. What part does leghaemoglobin in nitrogen fixation?
    It has a high affinity for oxygen and releases it in a controlled way for respiration but prevents the oxygen interfering with the nitrogen fixation reaction
  11. What is ammonification?
    Ammonification is when animals excrete nitrogen based products such as ammonia or urea, or animals and plants die, and their proteins are degraded by decomposers to ammonia
  12. Why is ammonia good to add to fertilisers?
    Ammonia adheres to soil particles such as clay meaning it is less soluble in water than nitrates.  Therefore, when it rains there will still be some fertiliser left on the fields
  13. What is nitrification?
    This is when ammonia is converted to nitrites (NO2) then nitrates (NO3)
  14. Which bacteria converts ammonia into nitrites?
    Nitrosomonas sp
  15. Which bacteria converts nitrites into nitrates?
    Nitrobacter sp
  16. What is assimilation?
    Assimilation is when plant roots absorb the nitrate/ammonia that was formed by nitrification/nitrogen fixation and incorporate it into plant proteins and nucleic acids
  17. What is denitrification?
    Denitrification is when some types of bacteria use nitrogen in the form of nitrites or nitrates to release energy from organic molecules, instead or using oxygen
  18. Why is denitrification a disadvantage to the ecosystem?
    As it releases all the nitrates back into the atmosphere as N2 which means the nitrogen cycle must begin again and the agricultural productivity of the soil is reduced.
  19. Why is denitrification an advantage to the ecosystem?
    As it stops large amounts of nitrogen from being leached into the water and causing harm to aquatic ecosytems
  20. Give an example of one type of bacteria that is involved in denitrification
    Pseudomas sp
  21. Draw the phosphorus cycle
  22. What is phosphours a main component of?
    Nucleic acids, phospholipids, ATP, bones, teeth
  23. What is the limiting factor of aquatic ecosystems?
    Phosphate availability
  24. What is eutrophication?
    Eutrophication results when the plants and algae eventually die, bacterial activity increases which reduces the oxygen in the water, so fish and other organisms eventually die