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Evidence for Evolution

Explore the direct and indirect evidence for evolution, including the fossil record, comparative anatomy, and molecular biology. Discover how these pieces of evidence support the theory of evolution and help scientists understand the history and relationships of different species.

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Evidence for Evolution

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  1. Evidence for Evolution

  2. Evidence For Evolution • Direct Evidence • Indirect Evidence

  3. Direct Evidence • Fossil Record - What you see is what you get! • Geographic Distribution of Living Species

  4. Comparison of Archaeopteryx to dinosaur and chicken.

  5. Fossil Record • By comparing fossils from older rock layers with fossils from younger rock layers, scientists can see how life on Earth has changed over time.

  6. Fossil Record • Hundreds of transitional fossils have been found which show intermediate stages of evolution of modern species from species now extinct this is an “incomplete record” with many gaps. Why are there so many “gaps” in the fossil record?

  7. Evolution of the Horse

  8. If this were where the horses were discovered what layer would you expect to see the most primitive horse?

  9. Burgess Shale

  10. What the….????

  11. Geographic Distribution of Living Species • Species living in different places with similar environments have similar anatomies and behaviors, even though they are unrelated. • L: Costa Rican Rainforest • R: African Rain Forest

  12. Indirect Evidence • Comparative Anatomy • Vestigial Structures • Embryology • DNA/Biochemical Evidence

  13. Homologous Body Structures • Homologous: develops from the same part of the embryo but have a different forms and functions (modified between groups) • Analogous: parts with similar functions which develop from different parts of the embryo (similar function, different structure) • (embryo is the early stage of development)

  14. Homologous Body Structures http://evolution.berkeley.edu/evolibrary/home.php

  15. Homologous Body Structures • Helps biologists group animals according to how recently they shared a common ancestor • Dolphins look more like fish but their homologies show they are mammals. They have lungs rather than gills and obtain oxygen from air, not water. (evolved from land mammals, not fish) • Phylogenetic trees show evolutionary relationships

  16. Analogous Structures

  17. Two major groups of mammals, marsupials and placentals, have evolved in a very similar way, even though the two lineages have been living independently on separate continents. • Australia separated from the other continents more than 50 million years ago, after marsupials had evolved but before the appearance of placental mammals.

  18. As a result, the only mammals in Australia (other than bats and a few colonizing rodents) have been marsupials, members of a group in which the young are born in a very immature condition and held in a pouch until they are ready to emerge into the outside world. Thus, even though placental mammals are the dominant mammalian group throughout most of the world, marsupials retained supremacy in Australia.

  19. Ichthyosaurs, Dolphins and Sharks • Living in the open ocean as a fish eater requires a streamlined body and the ability to move very quickly when needed. These pressures caused first sharks, then ichthyosaurs and finally dolphins, to all adopt a very similar body shape and method of movement.

  20. Phylogenetic TreesUnderstandinga phylogeny is a lot like reading a family tree. The root of the tree represents the ancestral lineage, and the tips of the branches represent the descendents of that ancestor. As you move from the root to the tips, you are moving forward in time.

  21. Vestigial organs • Organs so reduced in size that they no longer serve the function of homologous organs in related species • The presence of the organ does not affect its ability to survive and reproduce, so natural selection does not eliminate it

  22. Vestigial Structures • Examples: wings on flightless birds, human coccyx and appendix The appendix, for instance, is believed to be a remnant of a larger, plant-digesting structure found in our ancestors.

  23. Vestigial Structures • Left: A is normal fish versus B the Mexican Cave Dwelling fish with vestigial eye • Right: Blind cave salamander with vestigial eye

  24. Similarities in Embryology • All embryos develop similarly • Similar genes that define their basic body plan • ‘Tails’ as embryos • Embryos of all vertebrates especially similar; same groups of cells develop in same order and in similar patterns (homologous structures)

  25. “Real” Embryo PicturesTop Left=human 37 daysbelow= cattop= right dolphin

  26. Molecular Biology • All organisms use DNA and RNA to transmit genetic information • ATP is an energy carrier in all organisms. • You can compare the similar amino acid sequences (i.e. proteins) • Humans and Chimpanzees share 96% of the same DNA

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