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Descent With Modification Charles Darwin Traditional Views • • • • Earth is several thousand years old Forms remain unchanged Species composition remains unchanged Adaptation interpreted as genius design Evolutionary Adaptation • Accumulation of inherited characteristics that increase fitness Lamarck • Recognized examples of evolution taking place • Incorrect mechanism – Use and Disuse – Inheritance of acquired characteristics The Groundwork for Darwin’s Idea • Fossils • Geology Gradualism vs. Catastrophism • Catastrophism-Each boundary between fossil layers represents a natural disaster – Floods, droughts, fires • Gradualism- change is a slow process of accumulated traits • Uniformitarianism- Geologic features can be explained by current events • Grand Canyon/ Green River Darwin’s Influences • Medical School • HMS Beagle A Revolutionary Theory • On the Origin of Species by Means of Natural Selection- 1859 – Many species alive today are descendants of species that lived many years ago – Populations change when some individuals are more fit than others Adaptation • Could the accumulation of traits lead to new species? Descent with Modification • All living things descended from one ancestral organism • As populations moved into new habitats they were changed by the new conditions • Species that appear similar have a more recent common ancestor • Most branches are dead ends most species that have ever lived are now extinct Darwin’s observations • Variation within population • Overproduction of offspring • Most offspring don’t survive • Different phenotypes lead to different reproductive success Artificial Selection Natural Selection • Over production leads to competition for resources • Survival (successful competition) depends on inherited traits • Only those with the most useful traits will survive to reproduce • Offspring will more closely resemble successful individuals A Unifying Theory • Theory of natural selection explains a wide range of phenomena – Predator prey relationships – Camouflage – Similarities in DNA and protein sequences – Fossil record – Antibacterial resistance Cichlid fish Drug resistant TB • Drug regimen completion is rare • Surviving bacteria are the most resistant • Rebuild population • Multiple drug resistant strains of disease Homologies • Molecular homologies • Embryology • Homologous structures – Vestigial organs Homologous structures Vestigial structures Biogeography • Closely related species are found in the same areas – Australian marsupials • Island species are related to mainland species • Similar environments select for similar traits – Sugar glider and flying squirrel Fossil Record • Transitional species link ancient and modern forms Theories • Theory= a hypothesis that has stood up to testing, skepticism and extensive observations • “There is grandeur in this view of life…” On the Origin of the Species