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Chapter 15.3

Chapter 15.3. Evolution in Action. Case Study: Caribbean Anole Lizards. Often, scientists compare groups of organisms and look for patterns to group them better For example: Anole lizards in the Caribbean islands have different body types based on their environments

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Chapter 15.3

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  1. Chapter 15.3 Evolution in Action

  2. Case Study: Caribbean Anole Lizards • Often, scientists compare groups of organisms and look for patterns to group them better • For example: Anole lizards in the Caribbean islands have different body types based on their environments • Anole lizards that live mostly in trees have stocky bodies and long legs • Anole lizards that live on slender twigs usually have thin bodies, short legs and tails and large toe pads

  3. Anole Lizards • There are two hypotheses that could explain these similarities: • An ancestral anole species adapted for twigs lived on one island and migrated to other islands OR • Each twig-dwelling species evolved independently on each island from distinct anole ancestors • Both hypotheses were tested through DNA testing and the DNA evidence supported the second hypothesis • This process is known as convergent evolution

  4. Divergent Evolution • The model of the anole lizards can ALSO explain how the lizards adapted to different habitats • Long-legged trunk-dwellers can run faster and the short-legged twig-dwellers, but these could climb better • Both kinds of species on each island were closely related, but had become adapted to their own habitat: divergent evolution

  5. Adaptive Radiation • Sometimes, divergent evolution will happen to a new species in a new habitat until the population fills the space • This is called adaptive radiation • The anole lizards may have migrated to a new island and quickly evolved into several new populations/species in order to fill the new habitat • The fossil record indicates that adaptive radiation happened several times on the geologic time scale

  6. Artificial Selection • Darwin’s first chapter in On the origin of species… was about artifical selection • This is the process of choosing individuals in a population based on certain characteristics • Breeders of dogs and cats, farmers, etc do this a lot in order to get the best qualities into one “product” • With dogs: if we look into the genetics of dogs, we can see that all dogs descend from wolves in East Asia, where the first domestic dogs were selected from

  7. Coevolution • Evolution is an ongoing process and is happening all the time • Each species has forces of natural selection acting upon it • If two or more species evolve adaptations to each other’s influence (predator/prey for example), this is called coevolution • Flowering plants/insects, antibiotics/bacterial resistance, etc

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