Natural selection

• The process of evolution depends on a number of factors

  1. Organisms produce more offspring than can be supported by the environment -> over-production
  2. There is genetic variation within the population
  3. There is subsequently phenotypic variation within the population
• Natural Selection

  1. Organisms produce more offspring than can be supported
  2. Despite overproduction of offspring, population remains relatively constant because of intraspecific competition
  3. Within any population, there will be a gene pool containing a variety of alleles. Random mutations of alleles give individuals alleles that make them more likely to survive and reproduce
  4. These advantageous alleles are passed onto the next generations, making them more likely to survive and reproduce
  5. The frequency of advantageous alleles increases
• Summary of natural selection

  • Predation, disease and competition for the means of survival result in differential survival and reproduction
  • Those organisms with phenotypes providing selective advantages are more likely to produce offspring and pass on their favourable alleles to the next generation
  • This differential reproductive success causes changes in the allele frequencies within a gene pool