BY5.7 Energy

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Energy Source

  • the ultimate source of energy is the sun
  • the sun releases energy in the form of electromagnetic waves
  • most of the solar energy is reflected, absorbed or radiated back by the ozone layer, dust particles and clouds
  • 90% of the energy that penetrates the Earth's atmosphere and reaches the surrface is reflected by vegetation, sil and water or absrobed and radiated to atmosphere as heat
  • only 10% is available for producers to use
  • of the energy entering the plant between 15 and 5% is utilised by it
  • the rest is lost partly by reflection and by the evaportation of water

Trophic efficiency:

  • percentage of energy at one trophic level that is incorporated into the next one
  • rate at which energy passes into each trophic evel is about 10% of the energy at previous evels
  • known as the gross ecological efficiency
  • values differ between ecosystems

Energy flow through producers:

  • a large amount of energy that falls onto a plant is not absorbed
  • it is lost in 3 ways:
    • wavelength is wrong and so it is not absrobed
    • some light is refelcted
    • some light passes straight through wihtout hitting any chlorophylls



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