10.2 energy transfer in ecosystem

• how is energy transferred between trophic levels?

  • small amount of energy available is transferred to the next trophic level
• what is gross and net primary productivity?

  GPP =

  • rate at which producers make organic matter
  • energy taken in by the primary consumers
  • kgm-2year-1

  NPP =

  • energy transferred into biomass - available to the next trophic level
  • gpp - losses due to respiration
• why is some energy not taken to the next trophic level?


  • some parts of food not eaten
  • food not digested properly
  • plant doesn't absorb all light energy - wrong wavelengths
• why is some energy lost at each trophic level?

  • respiration
  • via heat given off to surroundings
  • energy passed on to other animals
• nitrogen cycle


  ->

  
• what are the role of microorganims in the nitrogen cycle?

  nitrogen fixing bacteria:

  • in the root nodules and soil.
  • convert nitrogen into ammonia
  • via nitrogenase enzyme

  nitrifying bacteria:

  • oxidise ammonia into nitrates
  • oxidation is exothermic - energy released to form ATP

  assimilation:

  • symbiotic fungi help mineral ions absorb
  • hyphae thinner than roots - large SA:Vol

  ammonification:

  • saprobionts decompose proteins in detritus into ammonia
  • ammonia converted into nitrates
• carbon cycle


  ->

  
• carbon cycle:


  1. plants photosynthesise and form organic matter - enters food chain
  2. respiration of animals, plants, decomposers - carbon dioxide returns into atmosphere
  3. combustion of fossil fuels - carbon dioxide released and dissolved into oceans
  4. plants undergo fossilisation - converts carbon dioxide into fossil fuels
• 2 types of decomposers

  • saprobionts
  • detritivores
• saprobionts


  • bacteria and fungi
  • live on detritus
  • use extracellular digestion to secrete (digestive) enzymes into detritus
  • absorb the soluble products
• detritivores


  • small invertebrate animals (earthworms, woodlice)
  • eat detritus
  • ingest detritus, digest it, absorb soluble product and excrete insoluble product
• how to calculate % efficiency

  (energy available after the transfer / energy available before) x 100