Biol 36
Chris Gillen
Lecture outline 6

Classification methodology (continued)

• Why is classification so difficult?
  • Many different characters can be used to classify animals
  • Only homologous characters should be compared
  • How can we know homologous structures?
  • Homologous structures can be very different
  • Analogous structures can be very similar
• Character state - the various conditions of a homologous character.
• The final problem is that many different methodologies exist for creating classifications
  • Numerical methods.
  • Cladistics. - 1966 Willi Hennig
    • derived and primitive characters
    • Example - mammals, primates
    • Parsimony
  • Traditional systematics.
• Example - vertebrate phylogeny

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