Biodiversity

• Species richness

  Measure of the number of different species in a community
• Biodiversity

  Species richness together with the number of organisms within each species in a geographical region
• As you move from the poles towards the equator

  Biodiversity increases
• Factors affecting biodiversity


  • Succession: the composition of a community changes over time as different species colonise
  • Natural selection
  • Human activity: pollution, overfishing, deforestation, farming
• Reductions in biodiversity are a concern because many plant species provide staple foods, raw materials, and drugs
• Simpson's diversity index

  An index of diversity that measures the number of individuals of each species and the number of species
• Polymorphic loci

  A gene's position on the chromosome that has two or more alleles that cannot be accounted for by mutation alone, resulting in two or more different phenotypes
• In some parts of the world, the frequency of the O allele is very high, accounting for over 99% of the gene pool. In other countries, the proportion of A and B alleles is much higher: this represents a higher biodiversity.
• Techniques to estimate the number of individuals of each species in a given area

  • Terrestrial animals: Mark-release-recapture, Population count index
  • Freshwater invertebrates: Kick sampling, use Simpson's Index
  • Plants: Quadrats and transects
• Sampling should be at random to eliminate sampling bias