4.6 Biodiversity within a community

• Biodiversity - The variety of living organisms in an area
• Biodiversity is the variety of living organisms in an area

  • Area measured could be local (small scale eg pond) or global (large scale eg amazon rainforest)
  • Local habitats are important as they support large numbers of species
  • Global biodiversity also important as it provides a baseline for scientists to monitor changes and identify what impact humans or climate change has
• Stable community - One where all the species and environmental factors are in balance so that population sizes remain fairly constant

  • Many organisms in ecosystems rely on one another, they are interconnected, so a drastic change in the number of organisms can have a large impact if community is unstable
• Genetic diversity - The variety of genes possessed by the individuals that make up a population of a species
• Measuring biodiversity: GENETIC DIVERSITY

  • The variety of genes making up an organism
  • Takes into account the different alleles that exist for those genes
  • Greater genetic biodiversity (more alleles) within a species increases variation and allows for better adaptation to a changing environment
  • This is because species with greater genetic biodiversity are more likely to survive changes to their environments, more likely to reproduce and allow species to survive
• Species richness - The number of different species in a community
• Measuring biodiversity: SPECIES RICHNESS

  • Number of different species living in an area
  • The more species present in a sample, the higher the species richness
  • It is measured by taking a random sample of a community and counting the number of species present
• Measuring biodiversity: SPECIES RICHNESS

  Problem:

  • Takes no account of the number of individuals of each species present
  • Two communities may have the same number of species but the proportions of the community made up of each species may differ
• Index of diversity:

  • Uses a formula which takes into account the species richness (number of species in a community) AND the abundance (number of individuals) of each species
• Index of diversity - Describes the relationship between the number of species in a community and the number of individuals in each species
• Index of diversity:

  • Greater species diversity index, the more stable an ecosystem is likely to be and less affected by change
• Index of diversity: FORMULA

  D = Index of diversity

  N = Total number of organisms of all species

  n = Total number of organisms of each species