Energy and ecosystems

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  • Energy and ecosystems
    • Food chains and foodwebs
      • Producers
        • Organism that synthesises organic molecules from simple inorganic ones.
        • 6CO2+6H2O=light energy+C6H12O6+6O2
      • Consumers
        • Any organism that obtains energy by 'eating' another
      • Decomposers
        • A group of organisms that break down comples material into simple components again releasing valuable minerals which cane be absorbed by plants.
        • Detritivores e.g. earthworms
        • Decompsors e.g. fungi and bacteria
      • Food chains
        • Describes a feeding relationship in which the producers are eaten by primary consumers....
        • Trophic level
          • The postion of an organism in a foodchain
    • Energy transfer between trophic levels
      • Suns energy
        • Reflected back into space
        • not all wavelenghts are absorbed and used for PS
        • light may not fall on a chlorophyll molecule
        • a factor may limit rate of PS
      • Net production=gross production-respiratory loss
        • Gross production
          • Total quantity of energy that the plants in a community convert to organic matter
        • some of the organism isn't eaten
        • Faeces
        • Exretary materials (urine)
        • Respiration
          • Mammals and birds because they need to maintain high body temperture
      • Relative inefficency of energy transfer between trophic levels explain why:
        • food chains mostly consisting of 4-5 trophic levels
        • Total mass of organismsin a paticular place (biomass) is less at higher trophic levels
        • total amount of energy stored is less at each level as one moves up a food chain
      • Calculating efficency of energy transferr
        • = energy available after transfer/energy available before the transfer x 100
    • Ecological pyramids
      • Number
        • no account is taken for size
        • number of individuals can be so great that its impossible to represent them accurately
      • Biomass
        • the total mass of the plants/animals in a particular place
        • fresh mass
          • water makes it unreliable
        • dry mass
          • animal needs to be dead
          • small samples= unrepresentative
        • grams per meter squared/cubed (if a volume
      • Energy
        • most accurate
        • collected in a given area, set period of time
          • kJm-2year-1
        • organisms of the same dry mass may store different amounts of energy
    • Agricultural ecosystem
      • trys to ensure much of the available energy from the sun is transferred to humans
        • Suns energy
          • Reflected back into space
          • not all wavelenghts are absorbed and used for PS
          • light may not fall on a chlorophyll molecule
          • a factor may limit rate of PS
      • Productivity
        • rate at which something is produced
        • Net productivity=gross productivity-respiratory loss
        • net productivity
          • efficiency of crop carrying out PS
          • area of ground covered by the leaves of the crop
      • energy input
        • food
        • fossil fuels
      • prevent climax community
    • pesticides
      • poisonous chemicals that kill pests
      • specific
      • biodegrade
      • cost effective
      • not accumulate
      • biological
        • specific
        • control organism can reproduce itself
        • pests dont become resistant
      • chemcial
        • effecct on non-target species
        • must be re-applied (expensive)
        • resistance
      • integrated pest control
        • emphasis on acceptable level of pest
        • animal or plant varieties that suit local area and pest resistant as possible
        • suitable habitats close to crops for natural predators
        • monitoring crop for signs of pests
        • removing pests by hand
        • using biological agents
        • using pesticides as a last resort
    • intensive rearing of domestic live stock
      • restricted movement
      • warm enviroment
      • controlled feeding
      • predators are excluded
      • selective breeding
      • growth hormones

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