BY4 - Population

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  • Population
    • Pest Control
      • Pests attack animals and crop plants which causes reduction in yield and a massive economic loss for farmers
      • How pests cause damage
        • Feeding on crops and animals
        • Competing with crop organisms for resources
        • Directly cause disease in crop organisms
      • Economic Injury Level
        • When pests cause so much damage it becomes worthwhile to invest in pest control
      • Chemical Control
        • Involves the use of herbicides, fungicides and insecticides to kill pests
        • Pesticides are poisonous.
          • Can be sprayed, used as powder or smokes in enclosed areas or added to animal feed
        • Insecticides are used to kill insects
          • They need to be specific, non-persistent and should not accumulate and be passed along food chains (bio-accumulation)
      • Advantages
        • Rapid eradication of pest over a specified localised area
        • Cheap
        • Fast acting and easy to apply
      • Disadvantages
        • Pests can develop resistance
        • Toxic to non-target organisms
        • Insecticides are non-specific
    • Biological Control
      • Exploitation of predator-prey relationships
      • A beneficial organism (AGENT) is deployed against an undesirable organism (TARGET).
        • Keeps pests below economic damage level
      • Aim: To reduce pest population to a more tolerable level  by artificially increasing the populations or the 'agent' organism
      • Completely eradicating the pest would be counter-productive because the predator would have no food source and would die out
        • And if the pest were to re-invade later on they would quickly increase to an economically damaging level
      • Advantages
        • Natural control method
        • Very specific
        • Cost effective if used long term
      • Disadvantages
        • Ultimately, you cannot control the predator you let loose into the pests environment
        • Slow process
        • Expensive to start up


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