Evidence For Evolution

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Evidence For Evolution

  1. 1. Evidence for Evolution Mark McGinley Associate Professor Honors College and Department of Biological Sciences Texas Tech University
  2. 2. Sir Peter Medawar Nobel Prize for Medicine 1960 <ul><li>“ It is naïve to suppose that the acceptance of evolution theory depends on the evidence of a number of so-called “proofs”; it depends rather upon the fact that evolutionary theory permeates and supports every branch of biological science, as much as the notion of the roundness of the earth underlies all geodesy and all cosmological theories upon which the shape of the earth has bearing. Thus, anti-evolution is of the same stature as flat-earthism.” </li></ul>
  3. 3. Buckets and Searchlights (Pennock) <ul><li>Search for understanding in science can occur in two ways- </li></ul><ul><li>- look for data that support your hypothesis </li></ul><ul><li>(put facts in a bucket) </li></ul><ul><li>- use hypothesis as a flashlight to illuminate new avenues of investigation </li></ul><ul><li>- some flashlights light up new avenues of understanding, other don’t </li></ul><ul><li>Evolution has been Biology’s most </li></ul><ul><li>powerful “searchlight ” </li></ul>
  4. 4. History of Evolutionary Thought <ul><ul><li>Plato (428-348 BC) </li></ul></ul><ul><ul><ul><li>idealism a. the &quot;idea&quot; is an eternal, unchanging essence </li></ul></ul></ul><ul><ul><ul><li>variation has no meaning, only essence matters </li></ul></ul></ul><ul><ul><li>Aristotle (384-322 BC) </li></ul></ul><ul><ul><ul><li>Scala Naturae or scale of nature </li></ul></ul></ul><ul><ul><ul><li>from inanimate to plants to animals to man- permanent, unchanging, everything fixed in place according to God's plan </li></ul></ul></ul><ul><ul><ul><li>The views of these two early Greeks prevailed for almost 2000 years. </li></ul></ul></ul>Aristotle
  5. 5. History of Evolutionary Thought <ul><ul><li>Carolus Linnaeus (1707-1778) </li></ul></ul><ul><ul><ul><li>1. father of taxonomy </li></ul></ul></ul><ul><ul><ul><li>2. defined fundamentals of biology in terms of nomenclature and classification </li></ul></ul></ul><ul><ul><ul><li>3. clustering groups into a hierarchy of increasingly general categories. </li></ul></ul></ul><ul><ul><ul><li>4. done for the greater glory of god - &quot;God's Registrar“ </li></ul></ul></ul><ul><ul><li>Buffon (1701-1788) </li></ul></ul><ul><ul><ul><li>1. French naturalist </li></ul></ul></ul><ul><ul><ul><li>2. large inheritance freed him from having to earn a living </li></ul></ul></ul><ul><ul><ul><li>3. suggested in 1779 that the earth might be very old (very heretical at the time) </li></ul></ul></ul><ul><ul><ul><li>4. forced to recant </li></ul></ul></ul><ul><ul><li>D. Cuvier (1769-1832) </li></ul></ul><ul><ul><ul><li>1. founder of paleontology - anatomist </li></ul></ul></ul><ul><ul><ul><li>2. observed that different strata of sedimentary layers contained different fossils. </li></ul></ul></ul><ul><ul><ul><li>3. catastrophism --explained changes in animal world in terms of catastrophes that had destroyed whole populations of living things in prehistoric times (floods etc.) </li></ul></ul></ul>Linneaus
  6. 6. Input from the Geologists <ul><ul><li>Hutton </li></ul></ul><ul><ul><ul><li>same processes are responsible for both past and present events - gradualism – </li></ul></ul></ul><ul><ul><ul><li>one of first to imply great age of the earth </li></ul></ul></ul><ul><ul><li>Lyell </li></ul></ul><ul><ul><ul><li>great champion of Hutton's work </li></ul></ul></ul><ul><ul><ul><li>Principles of Geology (1830)--greatly influenced Darwin even though he himself did not admit biological evolution </li></ul></ul></ul><ul><ul><ul><li>small forces acting over long periods of time can result in major changes e.g. destruction of mountains. Theory of uniformitarianism </li></ul></ul></ul>
  7. 7. Lamark <ul><ul><li>G. Lamarck (1744-1829) </li></ul></ul><ul><ul><li>the first uncompromising advocate of evolution, attempted to provide a mechanism to explain evolution </li></ul></ul><ul><ul><li>argued that lowly forms of life arise continually from inanimate matter by   spontaneous generation , and progress inevitably toward greater complexity and perfection </li></ul></ul><ul><ul><li>Mechanism of change was inheritance of acquired characteristics </li></ul></ul><ul><ul><li>emphasized great age of earth </li></ul></ul>
  8. 8. Charles Darwin <ul><li>“ The natural system based on descent with modification … the characters that naturalists consider as showing true affinity are those which have been inherited from a common parent, and in so far as all true classification is genealogical; that community of descent is the common bond that naturalists have been seeking.” </li></ul><ul><li>- Charles Darwin, Origin of Species, 1859 </li></ul>
  9. 9. Descent With Modification <ul><li>All organisms related through descent from some unknown ancestor that lived in the past </li></ul><ul><li>When descendents of that ancestor moved to new environments they accumulated new adaptations that allowed them to fit their new environment </li></ul><ul><li>Darwin’s proposed natural selection as the process responsible for these modifications </li></ul>
  10. 10. Descent With Modification- Darwin’s Finches
  11. 11. Descent With Modification
  12. 12. Descent With Modification
  13. 13. Descent With Modification
  14. 14. Patterns of Macroevolution
  15. 15. Geologic Timescale
  16. 16. Geologic Time Scale <ul><li>Earth formed about 4.6 billion years ago. That's 4,600,000,000 years which is a long long time (even older than my Mom)! </li></ul><ul><li>First life appeared 3.6-3.8 billion years ago. </li></ul><ul><li>How can we come to grips with that length of time? </li></ul>
  17. 17. Geologic Time Scale <ul><li>A football field is 100 yards long </li></ul><ul><li>If a football field equaled the age of the earth then </li></ul><ul><ul><li>each yard equals 46,000,000 years </li></ul></ul><ul><ul><li>each first down equals 460,000,000 years. </li></ul></ul>
  18. 18. Geologic Time Scale <ul><li>first microscopic life (3.6 bya) </li></ul><ul><ul><li>78 yards </li></ul></ul><ul><li>first multicellular life (900 mya) </li></ul><ul><ul><li>19.5 yards </li></ul></ul><ul><li>first land plants appear (450 mya) </li></ul><ul><ul><li>9.8 yards </li></ul></ul><ul><li>first appearance of dinosaurs (225 mya) </li></ul><ul><ul><li>4.9 yards </li></ul></ul><ul><li>the first appearance of H omo sapiens (1/2 mya). </li></ul><ul><ul><li>0.39 inch </li></ul></ul><ul><li>Domestication of dogs (~14,000 years ago) </li></ul><ul><ul><li>0.01 inch </li></ul></ul>
  19. 19. History of Life <ul><li>4.6 billion The Earth forms and is bombarded by meteorites and comets. </li></ul><ul><li>3.8 billion Replicating molecules (the precursors of DNA) form. </li></ul><ul><li>3.5 billion Unicellular life evolves. Photosynthetic bacteria begin to release oxygen into the atmosphere. </li></ul><ul><li>555 million Multi-cellular marine organisms are common. </li></ul><ul><li>500 million Fish-like vertebrates evolve. Invertebrates, such as trilobites, crinoids, brachiopids, and cephalopods, are common in the oceans. </li></ul><ul><li>450 million Arthropods move onto the land. Their descendants evolve into scorpions, spiders, mites, and millipedes. </li></ul><ul><li>420 million Land plants evolve, drastically changing Earth's landscape and creating new habitats. </li></ul><ul><li>360 million Four-limbed vertebrates move onto the land as seed plants and large forests appear. The Earth's oceans support vast reef systems. </li></ul>
  20. 20. History of Life <ul><li>250 million The supercontinent called Pangea forms. Conifer-like forests, reptiles, and synapsids (the ancestors of mammals) are common. </li></ul><ul><li>225 million Dinosaurs and mammals evolve. Pangea has begun to break apart. </li></ul><ul><li>130 million As the continents drift toward their present positions, the earliest flowers evolve, and dinosaurs dominate the landscape. In the sea, bony fish diversify. </li></ul><ul><li>65 million A massive asteroid hits the Yucatan Peninsula, and ammonites and non-avian dinosaurs go extinct. Birds and mammals are among the survivors. </li></ul><ul><li>4 million In Africa, an early hominid, affectionately named &quot;Lucy&quot; by scientists, lives. The ice ages begin, and many large mammals go extinct. </li></ul><ul><li>130,000 Anatomically modern humans evolve. Seventy thousand years later, their descendents create cave paintings — early expressions of consciousness. </li></ul>
  21. 21. Evidence for Evolution <ul><li>Hierarchical Organization of Life </li></ul><ul><li>The Fossil Record </li></ul><ul><li>Comparative Anatomy </li></ul><ul><li>Comparative Embryology </li></ul><ul><li>Molecular Biology </li></ul><ul><li>Biogeography </li></ul>
  22. 22. 1. Hierarchical Organization of Life <ul><li>There are lots of things that evolve over time from a common ancestor. </li></ul><ul><ul><li>Languages </li></ul></ul><ul><ul><ul><li>Linguists study evolution of languages </li></ul></ul></ul><ul><ul><li>Sports </li></ul></ul><ul><ul><ul><li>soccer=> rugby=>football </li></ul></ul></ul><ul><ul><ul><li>Football has different varieties </li></ul></ul></ul><ul><ul><ul><ul><li>Tackle vs. touch vs. flag </li></ul></ul></ul></ul><ul><ul><ul><ul><li>11 man vs. 6 man </li></ul></ul></ul></ul><ul><li>All can be organized in a hierarchical fashion. </li></ul>
  23. 23. Evidence from Hierarchical Organization <ul><li>Descent with modification predicts that life will be organized in tree-like, not linear manner. </li></ul>
  24. 24. Darwin’s Notebook
  25. 25. Tree of Life <ul><li>Descent with modification predicts a hierarchical organization of life </li></ul>
  26. 26. Hierarchical Organization <ul><li>Even Linneaus who didn’t believe that species evolved into new species recognized that species could be arranged hierarchically </li></ul>
  27. 27. Hierarchical Organization <ul><li>Dogs </li></ul><ul><ul><li>Share characteristics with wolves and coyotes </li></ul></ul><ul><ul><ul><li>Genus Canis </li></ul></ul></ul><ul><ul><li>Share characteristics with cats and weasels </li></ul></ul><ul><ul><ul><li>Order Carnivora </li></ul></ul></ul><ul><ul><li>Share characteristics with cows and mice </li></ul></ul><ul><ul><ul><li>Class Mammalia </li></ul></ul></ul><ul><ul><li>Share characteristics with insects and toads </li></ul></ul><ul><ul><ul><li>Kingdom Animalia </li></ul></ul></ul>
  28. 28. Hierarchical Organization
  29. 29. Hierarchical Organization <ul><li>Prediction </li></ul><ul><ul><li>Organisms that are more similar should have shared a more recent common ancestor. </li></ul></ul>
  30. 30. Chordate Phylogeny
  31. 31. 2. Evidence From the Fossil Record <ul><li>In the 17th century, Nicholas Steno noted the similarity between shark teeth and the rocks commonly known as &quot;tongue stones&quot;. </li></ul><ul><ul><li>first understanding that fossils were a record of past life. </li></ul></ul><ul><li>Later discovered large bones </li></ul><ul><ul><li>dinosaurs </li></ul></ul>
  32. 32. Fossil Record- Dating <ul><li>Relative dating places fossils in a temporal sequence by noting their positions in layers of rocks, known as strata. </li></ul><ul><ul><li>this principle is known as superposition </li></ul></ul><ul><li>Sometimes this method doesn't work, either because the layers weren't deposited horizontally to begin with, or because they have been overturned. </li></ul><ul><li>If that's the case, we can use one of three other methods to date fossil-bearing layers relative to one another </li></ul><ul><li>-faunal succession </li></ul><ul><li>- crosscutting relationships </li></ul><ul><li>- inclusions. </li></ul>
  33. 33. Fossil Record- Dating <ul><li>Numerical dating </li></ul><ul><ul><li>relies on the decay of radioactive elements, such as uranium, potassium, rubidium and carbon. </li></ul></ul><ul><ul><li>Very old rocks must be dated using volcanic material. By dating volcanic ash layers both above and below a fossil-bearing layer, as shown in the diagram, you can determine “older than X, but younger than Y” dates for the fossils. </li></ul></ul><ul><ul><li>Sedimentary rocks less than 50,000 years old can be dated as well, using their radioactive carbon content. </li></ul></ul>
  34. 34. Transitional Forms <ul><li>Prediction </li></ul><ul><ul><li>If current species arose from past ancestors then their should be evidence of transitional forms in the fossil record </li></ul></ul>
  35. 35. Beluga Whale
  36. 36. Ancestral Form- Pakicetus 50 mya
  37. 37. Transitional Form- Aetiocetus 25mya
  38. 38. Transition of Horse Feet
  39. 39. Horse Evolution
  40. 40. Missing Links <ul><li>Absence of evidence is not necessarily evidence of absence </li></ul>
  41. 41. 3. Evidence From Comparative Anatomy <ul><li>Descent with modification is supported by the anatomical similarities of species grouped in the same taxonomic category </li></ul><ul><li>Homologous Structures </li></ul><ul><ul><li>Similar structures derived from shared ancestry </li></ul></ul>
  42. 42. Homology of Vertebrate Fore-limbs
  43. 43. Homology of Mammalian Fore-limbs
  44. 44. Homologous Structures Whale vs. Hummingbird Skeletons
  45. 45. Homologous Structures-Plants
  46. 46. Homologous Structures-Cells
  47. 47. Vestigial Structures <ul><li>Descent With Modification </li></ul><ul><ul><li>Helps us understand the presence of vestigial structures </li></ul></ul><ul><li>Vestigial structures </li></ul><ul><ul><li>A type of homologous structure that is rudimentary and of marginal or no use to the organisms </li></ul></ul>
  48. 48. Vestigial Structures- Vestigial Legs Snakes Whales
  49. 49. 4. Evidence From Comparative Embryology <ul><li>Descent with modifcation explains the similarity between vertebrate embryos. </li></ul>
  50. 50. Comparative Embryology
  51. 51. Evidence From Comparative Embryology
  52. 52. 5. Evidence From Molecular Biology <ul><li>All life on earth shares a common genetic code! </li></ul><ul><ul><li>Strongest support for a single common ancestor. </li></ul></ul>
  53. 53. Evidence From Molecular Biology A aat tc g ctt cta gga atc tgc cta atc ctg B ... ..a .. g ..a . t . ... ... t .. ... .. a C ... ..a .. c .. c ... .. t ... ... ... t . a D ... ..a .. a .. g .. g .. t ... t . t .. t t .. Each amino acid difference in a protein or each nucleotide difference in DNA sequence is a character.
  54. 54. Molecular Evidence Building a Phylogenetic Tree
  55. 55. Evidence from Molecular Biology <ul><li>  In 1959, scientists at Cambridge University in the United Kingdom </li></ul><ul><ul><li>Myoglobin receives oxygen from hemoglobin and stores it in the tissues until needed. </li></ul></ul><ul><ul><li>Myoglobin has a single chain of 153 amino acids wrapped around a group of iron and other atoms (called &quot;heme&quot;) to which oxygen binds. </li></ul></ul><ul><ul><li>Observed in early 1960s that the structure of myoglobin was similar in all organisms. </li></ul></ul><ul><ul><li>Predict that organisms that are more closely related should have more similar AA sequence in their myoglobin. </li></ul></ul>
  56. 56. Molecular Evidence
  57. 57. Molecular Evidence
  58. 58. Molecular Evidence
  59. 59. Molecular Evidence
  60. 60. 6. Evidence From Biogegraphy <ul><li>What determines current patterns of marsupial distribution? </li></ul>
  61. 61. Biogeographic Evidence <ul><li>Fossils of marsupials have been found in the Antarctic as well as in South America and Australia. </li></ul><ul><li>During the past few decades scientists have demonstrated that what is now called South America was part of a large land mass called Gondwana, which included Australia and Antarctica. </li></ul><ul><li>Marsupials didn’t need a migration route from one part of the world to another; they rode the continents to their present positions. </li></ul>
  62. 62. Biogeographic Evidence Continental Drift <ul><li>Plate Tectonics is a “searchlight” idea in geology. </li></ul><ul><li>Biogeographers were early supporters of this idea because current distributions of animals and plants only made sense in light of this idea. </li></ul>
  63. 63. Human Evolution <ul><li>All of the lines of evidence that we have discussed should apply to human evolution as well. </li></ul>
  64. 64. Human Evolution

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