Evidence for Evolution

• Biogeography


  The observed geographic patterns of distribution of species
• Most evidence for evolution comes from biogeography
• Darwin's Hypothesis


  Evolution is the best explanation for why isolated islands had many species that were found nowhere else, and why these species bore a resemblance to species nearest the continent
• 1. Fossils closely resemble extinct organisms currently living in the same region; indicating that they could be ancestral. 
• 2. Many different species of finch found on the Galapagos Islands. They could have arisen from a single ancestral line and speciated due to isolation and filling different niches.
• 3. Homologous features: structures that share a common origin but may serve different functions in different species (ex. Whale and dolphin flipper bones and human hands); could indicate a common ancestor. 
• 4. Analogous features: features that serve the same purpose in different species, but are different in structure (e.g. Bat and bird wings, lobster and fish eyes).
• 5. Embryology: the embryos of many animals are structurally very alike during the beginning of development despite no relationship to function as the organism grows. 
• 6. Vestigial features and anatomical oddities: structures that are not used in living organisms (digits in dogs and horses, muscle for moving your ears, hips in whales); could indicate change over time.
• 7. Evidence of artificial selection: Darwin looked for a mechanism of inheritance through breeding. He found that variation was inheritable. 
• 8. In nature, the struggle for survival dictates breeding success. Darwin read Malthus’ “Essay on the Principle of Population” (1798) which stated that nature produces far more offspring than are needed to survive, and that population depends on resource availability. Darwin applied this to speciation: successful individuals that exploit resources best survive to reproduce, and pass on their traits to the next generation.