3.5.3 Energy and ecosystems

• Community - All the organisms of the different species living in the same habitat/ecosystem at the same time
• Producer - Photosynthetic organism - autotrophs. Transfer light energy (E) into chemical energy. Make organic molecules from inorganic molecules
• Consumer - Heterotrophs. Get their E from feeding on organic molecules
• Decomposer - Saprobiotic bacteria and fungi. Use organic molecules in faeces/urine/dead organisms
• Biomass - Mass of carbon per unit area per unit time . What's left over after respiration has used organic molecules
• Calorimetry - Technique to measure energy content of dry biomass
• Gross primary productivity (GPP) - total energy store in plant biomass
• Net primary productivity - Energy store in plant biomass minus respiratory losses
• NPP + R = GPP
• N - energy store in consumer
• N = I(energy ingested) - (F(faeces) + R(respiration))
• Energy lost due to photosynthesis:

  • Some light reflected
  • Not all wavelengths can be absorbed
  • Some light misses chlorophyll as heat
• Energy lost due to respiration:

  • Respiratory heat loss
  • Proton leakage across inner membrane
  • ATP used for active transport of protons in glycolysis/ Pyruvate into matrix
• Energy lost from producer to consumer:

  • Not all tissues eaten
  • Indigestible molecules
  • Respiratory heat loss
• Energy lost from consumer to consumer:

  • Respiratory heat loss
  • Not all tissues eaten
  • Indigestible molecules
• Farming practises which increases NPP of plants and N of animals:

  • Keeping animals indoors - reduces respiratory heat loss through reducing movement and maintaining body temperature
  • Control diet - less indigestible molecules
  • Simplify food chains - less biomass is lost between trophic levels
  • Herbicides - Reduce direct competition from weeds for nutrients and light
• Controls in calorimetry:

  • Air jacket to insulate - prevents heat loss
  • Stirrer - ensure an even distribution of heat
  • Non-conducting stand - prevent heat loss