Patterns of Evolution

Patterns of Evolution

1. Co-Evolution

   • Co-evolution is species evolving in response to each other
     • They are closely connected to one another by ecological interactions (have a symbiotic relationship), including...
       • Predator/Prey
       • Parasite/Host
       • Plant/Pollinator
     • Each party exerts pressures on the other, thereby affecting each others' evolution

2. Convergent Evolution

   • Convergent evolution is where similar selection pressures result in similar adaptations in species from different ancestors
   • Analogous structures are a result of this process (for example wings of bats, hawks, dragonflies)

3. Divergent Evolution

   • Divergent evolution is the process in which a trait held by a common ancestor evolves into different variations over time
     • This process results in adaptive radiation and therefore speciation
   • Homologous structures are a result of this process (e.g. whale flippers, frog forelimbs)

4. Gradualism

   • When conditions change very slowly, the selection pressure is not very intense
     • This means that while some individuals will have a greater chance of reproductive success, any change in allele frequency will occur over a long period
       • This results in a gradual change of the species

5. Punctuated Equilibrium

   • Sudden changes in niche availability or environmental changes after a long period of stasis (no change) can lead to periods of rapid evolutionary change
   • FOR EXAMPLE with the introduction of a species to a new place, such as Dracophyllum to New Zealand, the one species has a number of new niches, each with its own selection pressures - causing sudden speciation

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