Convergent Evolution (SL IB Biology)

Convergent evolution

• Analogous structures are characteristics with similar form and function, but with different evolutionary origin
  • Such structures have historically caused some confusion for scientists working in the field of taxonomy
• While homologous structures provide evidence of shared ancestry, analogous structures come about as the result of convergent evolution
  • Analogous structures provide evidence for the passing on of advantageous characteristics during natural selection
• Convergent evolution can occur when two distantly related species live in habitats with similar selection pressures, meaning that similar characteristics provide a survival advantage
  • Advantageous characteristics evolve separately, rather than as the result of a single mutation
• Examples of similarities that have arisen due to convergent evolution include:
  • Dolphins and sharks
    • These are both groups of aquatic animals that share a similar body shape, but they in fact belong to different classes
      • Dolphins are mammals and sharks are fish
    • Their streamlined body shapes evolved separately rather than originating in one common ancestor
  • Cacti and euphorbia
    • These are two groups of desert plants recognisable by their spiny leaves and branching, succulent stems
    • They belong to different orders of plants
      • Cacti are found in the deserts of the Americas, while euphorbias are found in Africa
    • They evolved separately, but adapted to similar environments

Analogous structures diagram

Analogous structures, such as body shape in sharks and dolphins, and wings in butterflies and bats, occur as the result of convergent evolution