Energy and Ecosystems

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  • chemical and biological control of agricultral pests
    • pests
      • organism that competes with humans for food or space.
      • reduce productivity
        • weeds competition forwater minerals
        • insects damage crops eating them.
    • pesticides
      • biodegradable so it will break down into harmless substances in the soil but needs to be chemically stable so has a long shelf life  
      • cost effective
      • be specific harmless to humans and other organsims
      • not accumulate - causing bioaccumulation
    • biological control
      • aim to control not eradicate
        • could be counter productive so not enough pest for predator, pest numbers increase.
      • controlling a pest by using its natural predator or parasites of it
      • disadvantages
        • control may become pest itself
        • do not act as quickly time between introduction and significant control
    • comparison of biological and chemical control
      • biological
        • pests don't become resistant
        • very  specific
        • control organism reproduces itself
        • control could become pest feed on crops due to low pest population
      • chemical pesticides
        • pests can develop genetic resistance
          • new pesticides have to be developed
        • must be re-applied - expensive
        • risk of bioaccumulation and eutrophication
        • always have  some effect on other species
    • integrated pest control systems
      • minimum impact on environment
      • involves
        • manually remove pests
        • monitor crops for early pests.
        • use biological control if necessary
        • manage environment to provide habitats for preadators
        • last resort: pesticides
        • use immune plant/ animal to a pest
      • chemical biological and natural methods


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