Review: Why Evolution Is True

7. The Origin of Species

  • How do species arise from natural selection?
    • A species get split by geographical isolation
      “the theory of geographic speciation”
    • Both groups continue to evolve independently
  • Different species cannot exchange genes
    • They are “reproductively isolated”
    • Biological Species Concept (BSC)
      • “a reproductive gene pool”
  • Species are “evolutionary accidents”
  • Species do not arise to fill empty niches
  • There has been enough time for speciation to create millions of species
  • Sister species tend to be geographically close
  • Speciation can be seen happening
    • Creationists often claim that if we can’t see a new species evolve during our lifetime, then speciation doesn’t occur. But this argument is fatuous: it’s like saying that because we haven’t seen a single star go through its complete life cycle, stars don’t evolve, or because we haven’t seen a new language arise, languages don’t evolve.”
  • Reproductive isolation increases over time
  • Sympatric speciation is rare as expected
    Sympatric speciation: Different species occur in close proximity to each other

    • Subset: Hybridisation can produce new species
      Chromosomes are doubled—a random event with low frequency, but not low probability in species (usually plants) that produce millions of eggs/sperm.

      • Allopolyploid speciation
      • Polyploid speciation

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  1. […] The variety of life is explained by the Theory of Evolution; the evidence for which is overwhelming. […]

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