Trophic Levels, Food Webs and Food Chains

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  • Trophic Levels, Food Chains & Food Webs
    • Trophic Levels are energy levels in a food chain.
      • Level 3- Carnivores
        • E.g. house sparrow, fish
      • Level 2- Herbivores
        • E.g. earthworm, zooplankton
      • Level 4- Top Predators (Omnivores)
        • E.g. tawny owl, great white shark
      • Level 1- Autotrophs
        • E.g. grass, phytoplankton
    • Reducer Organisms operate at all trophic levels. They return remaining nutrients to the soil.
      • Deritovores- animals which eat dead or decaying organisms
        • E.g. lice, earthworms, vultures
      • Decomposers- organisms which cause the decay of dead plants, animals and excrement
        • E.g. bacteria, fungi
    • Energy Pyramids
      • In an ecosystem, nutrients are recycled but 90% of energy is lost at each trophic level.
        • Therefore, there is less energy (insolation) available at each trophic level, so fewer organisms can be supported.
          • This energy loss can be illustrated using energy pyramids
    • Food Webs/Chains
      • Food chains are useful for explaining the basic principals behind an ecosystem. However, they only show one species per trophic level which is rarely the case in reality.
      • A more realistic version of an ecosystem can be shown using a food web (a network of linked food chains)

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