3.7.3: Evolution may lead to speciation

• Variation:

  • Differences between individuals
  • Individuals of the same species have same genes but different alleles -> genetic variation within species
• Sources of variation

  • Mutation -> changes in DNA base sequence -> new alleles
  • Meiosis -> crossing over of chromatids & independent assortment/segregation of (homologous) chromosomes
  • Random fertilisation of gametes during sexual reproduction
  • Environment (mutagenic agents / LINKS TO GENE EXPRESSION)
• Evolution

  • A change in allele frequencies over time