biodiversity

• Biodiversity


  The variety of different species and their relative abundance in a given community or ecosystem
• Measures of biodiversity


  • Species diversity (number of different species and individuals within each species)
  • Genetic diversity (variety of genes amongst individuals in a population)
  • Ecosystem diversity (range of different habitats)
• 1. level biology focuses on species diversity, particularly species richness (number of different species in a particular area at a particular time)
• Importance of biodiversity


  • Can describe a range of habitats
  • Low biodiversity not necessarily a cause for concern (e.g. in harsh environments)
  • Decrease in previously high biodiversity is a concern, often caused by human activity
• Farming practices that reduce biodiversity

  • Destruction of hedgerows
  • Selective breeding
  • Monoculture
  • Overgrazing
  • Draining wetlands
• Compromises to conserve biodiversity while enabling farming

  • Retaining some hedgerows
  • Selective breeding in limited areas
  • Crop rotation
  • Mixed cropping
• Index of diversity


  Measure of biodiversity that considers both the number of species and the relative abundance of each species
• Species richness


  Number of different species in a particular area
• Calculating Simpson's index of diversity

  1. N = total number of organisms

  2. n = population size of one species

  3. Sum (n(n-1))

  4. N(N-1)
• Simpson's index of diversity typically falls between 3 and 6