Biodiversity - Chapter 17 AQA AS Biology

Chapter 17 - AQA AS Biology 

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  • Created by: H.N
  • Created on: 30-12-12 19:47
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  • Biodiversity
    • Genetic diversity = variety of genes possessed by the individuals that make up any 1 species
    • Biodiversity = general term to describe variety in the living world
    • Ecosystem diversity = range of different habitats within a particular area
    • Species Diversity
      • Species diversity = the no. of different species + the no. of individuals within a community
      • measuring species diversity
        • no. of different species in a given area
        • proportion of the community made up of an individual species
        • d = N(N-1) / {n(n-1)
          • Key:
            • d= species diversity index
              • N= total no. of organisms of all species
                • n= total no. of organisms of each species
                  • { = the sum of
          • the higher the value of 'd', the greater the species diversity
      • higher the species diversity index - the more stable an ecosystem  + the less its affected by climate
    • Impact of agriculture
      • farmers select species for particular qualities that make them more productive
        • no. of species + variety of alleles possessed is reduced to the few with the desired features
      • any area can only support a certain amount of biomass
        • if large amount taken up by 1 species then less space for other species
          • competition for space + resources - many won't survive
      • pesticides used to exclude other species
      • reduction in species diversity = low species diversity index in agricultural ecosystems
    • Impact of deforestation
      • tropical rain forests - highest species diversity
      • some due to accidental fires, but vast majority due to human actions
        • sometimes due to man- made pollutants producing acid rain
      • Deforestation = the permanent clearing of forests and the conversion of land to other uses e.g. agriculture, grazing, housing + reservoirs
      • loss of biodiversity, reduced species diversity
        • even new forests grown for commercial purposes have just a few predominant tree types
  • { = the sum of
  • higher the species diversity index - the more stable an ecosystem  + the less its affected by climate


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