• alleles - different versions of the same gene
  • genetic diversity—number of different alleles that exist in a species
  • species with a greater genetic diversity will better adapt to their environment and be more resistant to to environmental change and therefore less likely to become extinct

Factors affecting genetic biodiversity

  • to increase biodiversity the number of alleles within a species must increase. This can happen via:
    • mutations
    • gene flow: interbreeding between different populations leads to alleles crossing between distinct groups
  • genetic diversity can also decrease, this can happen via:
    • selective breeding: selected characteristics are bred for
    • captive breeding programmes: only a small number of individuals (and therefore alleles) available for breeding.
    • rare breeds: difficult to maintain high numbers of individuals but also meet requirements for that rare breed
    • artificial cloning: eg tissue cultures or cuttings in plants
    • natural selection: species evolve to only have beneficial alleles so less advantageous ones are lost
    • genetic bottlenecks: when only a few individuals survive environmental change such as a disease meaning the gene pool is reduced
    • founder effect: when a small number of individuals create a new colony and are isolated from the original population
    • genetic drift: due to random nature of which alleles do/don’t get passed on during sexual reproduction

Measuring genetic biodiversity

  • polymorphic genes: genes that have more than one allele

  • monomorphic genes: a single allele exists

  • locus/loci: position of a gene/genes on a chromosome

  • the proportion of genes that are polymorphic can be calculated by:

    • (number of polymorphic gene loci/ total number of loci) x 100
  • the greater the proportion of polymorphic loci, the greater the genetic diversity