Chapter 22b (Class)


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Chapter 22b (Class)

  1. 1. 2007-2008<br />Evidence of Evolutionby Natural Selection<br />Dodo bird<br />
  2. 2. Evidence supporting evolution<br />Fossil record<br />transition species <br />Anatomical record<br />homologous & vestigial structures<br />embryology & development<br />Molecular record<br />protein & DNA sequence<br />Artificial selection<br />human-caused evolution<br />
  3. 3. Fossil record<br />Layers of sedimentary rock contain fossils <br />new layers cover older ones, creating a record over time<br />fossils within layers show that a succession of organisms have populated Earth throughout a long period of time<br />
  4. 4. Fossil Record<br />
  5. 5. Fossil record<br />A record showing us that today’s organisms descended from ancestral species<br />
  6. 6. Evolutionary change in horses<br />550<br />500<br />450<br />Equus<br />400<br />350<br />Body size (kg)<br />300<br />250<br />Merychippus<br />200<br />Mesohippus<br />150<br />Hyracotherium<br />100<br />50<br />Nannippus<br />60<br />55<br />50<br />45<br />40<br />35<br />30<br />25<br />20<br />15<br />10<br />5<br />0<br />Millions of years ago<br />
  7. 7. Evolution of birds<br />Archaeopteryx<br />lived about 150 mya<br />links reptiles & birds<br />Smithsonian Museum, Washington, DC<br />
  8. 8. ?<br />?<br />?<br />?<br />Land Mammal<br />Where are thetransitional fossils?<br />
  9. 9. 2006 Fossil Discovery of Early Tetrapod<br />Tiktaalik<br />“missing link” from sea to land animals<br />
  10. 10. Homologous structures<br />similarities in characteristics resulting from common ancestry<br />Anatomical record<br />
  11. 11. Homologous structures<br />Similar structure<br />Similar development<br />Different functions <br />Evidence of close evolutionary relationship<br />recent common ancestor<br />
  12. 12. spines<br />leaves<br />succulent leaves<br />tendrils<br />colored leaves<br />Homologous structures<br />needles<br />
  13. 13. Analogous structures<br /><ul><li>Separate evolution of structures
  14. 14. similar functions
  15. 15. similar external form
  16. 16. different internal structure & development
  17. 17. different origin
  18. 18. no evolutionary relationship</li></ul>Don’t be fooledby their looks! <br />Solving a similar problem with a similar solution<br />
  19. 19. Convergent evolution<br />Flight evolved in 3 separate animal groups<br />evolved similar “solution” to similar “problems”<br />analogous structures<br />Does this mean they have a recent common ancestor? <br />
  20. 20. Convergent evolution<br /><ul><li>Fish: aquatic vertebrates
  21. 21. Dolphins: aquatic mammals
  22. 22. similar adaptations to life in the sea
  23. 23. not closely related</li></ul>Those fins & tails <br />& sleek bodies areanalogous structures!<br />
  24. 24. Parallel Evolution<br />Convergent evolution in common niches<br />filling similar ecological roles in similar environments, so similar adaptations were selected<br />but are not closely related<br />marsupial <br />mammals<br />placental <br />mammals<br />
  25. 25. Parallel types across continents<br />Niche<br />Placental Mammals<br />Australian Marsupials<br />Burrower<br />Marsupial mole<br />Mole<br />Anteater<br />Numbat<br />Anteater<br />Nocturnal<br />insectivore<br />Marsupial mouse<br />Mouse<br />Climber<br />Spotted cuscus<br />Lemur<br />Sugar glider<br />Glider<br />Flying<br />squirrel<br />Stalking<br />predator<br />Tasmanian cat<br />Ocelot<br />Chasing<br />predator<br />Wolf<br />Tasmanian “wolf”<br />
  26. 26. Vestigial organs<br />Modern animals may have structures that serve little or no function<br />remnants of structures that were functional in ancestral species<br />deleterious mutations accumulate in genes for non-critical structures without reducing fitness<br />snakes & whales — remains of pelvis & leg bones of walking ancestors<br />eyes on blind cave fish<br />human tail bone<br />This is notLaMarck’s loss from “disuse”!<br />
  27. 27. Vestigial organs<br />Hind leg bones on whale fossils<br />Why would whaleshave pelvis & leg bonesif they were alwayssea creatures?<br />
  28. 28. Comparative embryology<br />Similar embryological development in closely related species<br />all vertebrate embryos have similar structures at different stages of development <br />gill pouch in fish, frog, snake, birds, human, etc.<br />
  29. 29. Molecular record<br />Human/kangaroo<br />100<br />Human/<br />cow<br />Dog/<br />cow<br />75<br />Rabbit/<br />rodent<br />Human/rodent<br />Llama/<br />cow<br />Horse/<br />donkey<br />50<br />Nucleotide substitutions<br />Horse/cow<br />Sheep/<br />goat<br />Pig/<br />cow<br />25<br />Goat/cow<br />0<br />0<br />25<br />50<br />75<br />100<br />125<br />Millions of years ago<br />Comparing DNA & protein structure<br />universal genetic code! <br />DNA & RNA<br />compare common genes<br />cytochrome C (respiration)<br />hemoglobin (gas exchange)<br />Why comparethese genes?<br />Closely related species have sequences that are more similar than distantly related species<br /><ul><li>DNA & proteins are a molecular record of evolutionary relationships</li></li></ul><li>Comparative hemoglobin structure<br />Dog<br />Lamprey<br />Frog<br />Bird<br />Macaque<br />Human<br />Why does comparingamino acid sequencemeasure evolutionaryrelationships?<br />32<br />8<br />45<br />125<br />67<br />10<br />0<br />20<br />30<br />40<br />50<br />60<br />70<br />80<br />90<br />100<br />110<br />120<br />Number of amino acid differences between<br />hemoglobin (146 aa) of vertebrate species and that of humans<br />
  30. 30. Building “family” trees<br />Closely related species (branches) share same line of descent until their divergence from a common ancestor<br />
  31. 31. Artificial selection<br />Artificial breeding can use variations in populations to create vastly different “breeds” & “varieties”<br />“descendants” of wild mustard<br />“descendants” of the wolf<br />
  32. 32. Natural selection in action <br />Insecticide & drug resistance<br />insecticide didn’t kill all individuals<br />resistant survivors reproduce<br />resistance is inherited<br />insecticide becomes less & less effective<br />
  33. 33. 2007-2008<br />"Nothing in biology makes sense except in the light of evolution."<br />-- Theodosius DobzhanskyMarch 1973<br />Geneticist, Columbia University<br />(1900-1975)<br />
  34. 34. 2007-2008<br />Evolution is "so overwhelmingly established that it has become irrational to call it a theory."<br />-- Ernst Mayr What Evolution Is2001<br />Professor Emeritus, Evolutionary Biology <br />Harvard University<br />(1904-2005)<br />
  35. 35. 2007-2008<br />Don’t be a Dodo…<br />Ask Questions!!<br />