(3) Genetic Diversity

• organisms of the same species have very similar genomes, but all individuals (even identical twins) have some form of genetic variation
• Genetic variation = differences in DNA base sequences between individuals of a species
• mutations cause genetic variation
• all members of the same species have the same genes (eg gene for blood group)
• the differences are within the alleles of a gene
• alleles = different forms of a gene
• genetic variation is passed on to offspring through the process of meiosis and sexual reproduction and results in genetic diversity within a species population
• gene pool = the different alleles in a population
• genetic diversity = number of different alleles in a population
• the new alleles may be advantageous, disadvantageous or hae no effect on the phenotype (introns/ degenerate)
• variation is necessary for natural selection
• natural selection leads to evolution
• Natural Selection 1 :

  • there is variation between a population of individuals called a gene pool (sum of different alleles in a population)
• Natural Selection 2 :

  • random DNA mutations may result in a new allele (exons) - different form of a gene
• Natural Selection 3 :

  • the new allele is beneficial to the individuals within the population
  • may produce a protein which provides resistance to an environmental factor
• Natural Selection 4 :

  • the individuals are more likely to survive within the environment selection pressure
  • selective advantage
• Natural Selection 5 :

  • as the individual are living a longer life, they are more likely to successfully reproduce
• Natural Selection 6 :

  • passing the new beneficial allele into the offspring
• Natural Selection 7 :

  • over many generations the beneficial allele becomes more prevalent within the population
  • allele increases in frequency
• a population with a larger gene pool or high genetic diversity has a strong ability to adapt to change - evolve
• a population with a smaller gene pool or low genetic diversity can become vulnerable to extinction
• smaller gene pool = too similar
• limited ability to adapt to environmental change in increasing the risk of extinction
• gene flow = transfer of genes between populations (non-related)