Micro-evolution

Mutation

• genome is collection of DNA sequences that code for traits
• DNA can be altered by ionization
  ionizing radiation (such as UV),
  chemically induced,
  random error
  • nucleotide removed from deoxyribose backbone
  • if DNA is double helix, repair is possible
    by base-pairing during repair
  • when DNA is single stranded, repair may be quasi-random
    resulting in incorrect sequence, and potentially erroneous code
• erroneous code may produce 'defective proteins'
  • frequently confers disadvantage,
    and mutation is removed from population by natural selection
  • when mutation confers advantage
    natural selection will reduce numbers of 'wild-type' phenotype
• description of species may therefore change over time
  although species remains same species
• there are numerous documented examples of micro-evolution

Macro-evolution

• refers to the process by which mutation can produce new species
• Darwinian thinking suggested that accumulation of modified traits over time
  would lead to the production of species
• current thinking suggests that there must be a isolating mechanism
  for a sub-population of one species can become a new species
  • reproductive isolation
    • geographic barriers
    • ecological barriers
    • temporal barriers
    • mechanical barriers
• In plants:
  • hybridization
  • autopolyploidy

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