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Evidence for Evolution

Evidence for Evolution. Part III. Fossil Evidence: Summary. Rock strata ordered bottom to top, shows fossils oldest to youngest

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Evidence for Evolution

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  1. Evidence for Evolution Part III

  2. Fossil Evidence: Summary • Rock strata ordered bottom to top, shows fossils oldest to youngest • Oldest fossils are simpler (single-celled organisms, jawless fish, etc); newer fossils show more complex structures (vertebral columns, ear bones, etc) and more closely resemble current species on planet • Species with common traits are found in adjacent rock strata • Fossils dated using radiometric dating based on half-lives of radioactive elements/isotopes; different elements provide accurate dates over different time spans • Fossil record has predictive ability: darwin predicted the existence of transitional forms like tiktaalik the “walking fish” (fish-amphibian intermediate) before these fossils were discovered

  3. Biogeography • Geographical patterns in the distribution of living and fossilized species provide evidence for evolution • Darwin made many observations while in the Galapagos regarding the distribution of living and fossilized species; he believed evolution provided the best explanation for these observations • Similar species found in similar ecosystems

  4. Biogeography

  5. To What Species does this Embryo belong? Gill Slits Tail Bud Limb Buds

  6. Embryological Evidence • Striking similarities between embryos of all species • Human embryonic structures, such as tail and lanugo, disappear before birth (usually)

  7. Anatomic Evidence: Vestigial Structures • Vestigial Structures – A structure that no longer performs the function for which it was intended but provides clues about ancestry • Examples of vestiges: • Flightless birds • Whale pelvis and legs • Eyes of moles, cave dwellers such as fish & salamanders • Dew claws of dogs

  8. Anatomic Evidence: Vestigial Structures • Human Vestigial Structures • appendix • arrectorPili Muscles • tail

  9. Comparative Anatomy • Homologous and Analogous Features • Homologous – Structures that perform different functions but have the same basic design • These structures arose at one point in history and shows that species share a more recent common ancestor

  10. Comparative Anatomy (Cont.) • Analogous – Structures that perform the same functions but show very little structural similarity • These structures arose independently of one another and these species are more closely related

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