notes

• evolution

  • changes in the heritable characteristics of an organism over generations
  • heritable characteristics are determined by alleles of genes
• evolution via natural selection
• evolution via natural selection

  1. variation is present in a population, mutations causing different phenotypes, mutation via meosis
  2. selection pressures affect a population eg food availability, predation and disease
  3. those with advantageous alleles more likely to survive and reproduce
  4. thus advantageous allele is passed onto offspring
  5. advantageous alleles become more frequent in a population, increasing in frequency in the gene pool
• natural selection

  process by which organisms are better adapted to their enviro in order to survive, reproduce and pass on advantageous allele
• speciation

  • the development of new species from pre-existing species overtime
  • 2 populations must be isolated from eachother, with no exchange of genes
• allopatric speciation

  1. population of species become seperated from eachother via a geographical barrier
  2. no gene flow taking place as no interbreeding
  3. different selection pressures or accumulation of random changes means allele frequencies in gene pools for both populations may be different
  4. changing allele frequencies- changing phenotypes of both populations
  5. eventually no longer able to breed with eachother and produce fertile offspring- seperate species
• sympatric speciation

  1. random changes in alleles and thus phenotypes of individuals in population, prevents successful interbreeding
  2. lack of gene flow between 2 populations means allele frequencies in gene pools of 2 pops may change in different ways
  3. changes in allele frequencies= changes in phenotypes of the 2 populations
  4. 2 populations eventually no longer able to breed with eachother to produce fertile offspring= seperate species