Patterns of Evolution

• Adaptive Radiation


  Occurs when a single species evolves into a number of distinct, but closely related species. Each species fills a different ecological niche.
• Adaptive Radiation


  • 13 species of finch birds live in the Galapagos Islands
• Divergent Evolution


  Large-scale evolution of a group into many different forms. Favoured by natural selection.
• Divergent Evolution


  • Ontario has over 20 species of closely related rodents like deer mouse, flying squirrel, porcupine & beaver
• Convergent Evolution


  Occurs when two or more species become increasingly similar in phenotype in distantly related species.
• Convergent Evolution


  • Sharks and Dolphins have similar body shapes
• Homoplasies


  Similar traits found in two or more different species, resulting from convergent evolution or from reversals, not from common descent; also called analogous features
• Homoplasies


  • Both sharks and dolphins have very similar streamlined bodies well suited for high speed
• Coevolution


  Coevolution exists when two species are dependant on each other for their survival. As species coevolve, one or both species may become increasingly dependent on the other.
• Coevolution


  • Brazil nut trees have evolved extremely hard protective shells, while the agouti (rodent) is the only mammal with jaws and teeth strong enough to bite open the shell