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  1. 1. Evolution Descent with Modification
  2. 2. Evolution Overview <ul><li>The framework for modern biology </li></ul><ul><li>Definition: </li></ul><ul><ul><li>a change over time </li></ul></ul><ul><li>Occurs in populations, not individuals </li></ul><ul><li>How new organisms are created </li></ul><ul><li>A theory subject to revision and change </li></ul><ul><li>A hot topic long before Darwin & Wallace suggested a mechanism </li></ul>
  3. 3. Darwin’s Big Ideas <ul><li>Darwin, in Origin of the Species , made 2 revolutionary points: </li></ul><ul><ul><li>species are not created 'as is', but evolve from ancestral species </li></ul></ul><ul><ul><li>proposed mechanism to account for changes in species: </li></ul></ul><ul><ul><li>Natural Selection </li></ul></ul>
  4. 4. History – Before Darwin <ul><li>Context before Darwin: </li></ul><ul><li>Believed organisms were created 'as is'; immutable </li></ul><ul><li>Nature was like a ladder - man on the top rung </li></ul><ul><li>Earth thought to be 5 - 6,000 years old. </li></ul><ul><li>Linneaus - 18th C. </li></ul><ul><ul><li>developed classification scheme </li></ul></ul><ul><ul><li>based on similarities, hierarchy </li></ul></ul><ul><ul><li>did not subscribe to evolutionary relationships </li></ul></ul>
  5. 5. Early Evolutionary Ideas <ul><li>Georges Buffon - 1749 </li></ul><ul><ul><li>French scientist </li></ul></ul><ul><ul><li>suggested the age of the earth was underestimated </li></ul></ul><ul><ul><li>living things had changed </li></ul></ul><ul><li>Jean Baptiste de Lamarck - 1809 </li></ul><ul><ul><li>proposed a theory of evolution </li></ul></ul><ul><ul><li>called his idea &quot;the parade of nature&quot; </li></ul></ul><ul><ul><li>organisms were continually ascending and acquiring more perfect characteristics </li></ul></ul>
  6. 6. Lamarck’s Key Ideas <ul><li>Use and disuse of organs varies </li></ul><ul><li>Shaping force was environment </li></ul><ul><li>Organisms respond to changes in their environment by developing or changing their structure </li></ul><ul><li>Inheritance of acquired traits </li></ul><ul><li>Once highly respected </li></ul><ul><ul><li>couldn't support his ideas, fell in disfavor </li></ul></ul>
  7. 7. Lamarckian Evolution
  8. 8. Charles Darwin <ul><li>Living things evolve to adapt to their environment </li></ul><ul><li>Thinking shaped by his experiences </li></ul><ul><ul><li>Naturalist aboard H.M.S. Beagle at age22 </li></ul></ul><ul><ul><li>Read Charles Lyell </li></ul></ul><ul><ul><ul><li>earth much older </li></ul></ul></ul><ul><ul><ul><li>physical forces that shaped the earth still exist </li></ul></ul></ul><ul><ul><li>Saw similar species on the Galapagos Islands </li></ul></ul><ul><ul><ul><li>realized they must have come from mainland and gradually become new species </li></ul></ul></ul><ul><ul><li>Collected much data, but didn't publish for 20 years </li></ul></ul><ul><ul><li>Eventually presented his work with Alfred Russell Wallace </li></ul></ul><ul><ul><li>Published Origin of the Species </li></ul></ul><ul><li>Proposed different mechanism to account for changes: Natural Selection </li></ul>
  9. 9. Voyage of the Beagle
  10. 10. The Basis of Darwin’s Theory <ul><li>Variation exists within species </li></ul><ul><ul><li>traits vary among individuals of the same species </li></ul></ul><ul><li>All organisms compete for limited natural resources </li></ul><ul><ul><li>some will get more, some less (Malthus) </li></ul></ul><ul><li>Organisms produce more offspring than can survive </li></ul><ul><ul><li>leads to competition </li></ul></ul><ul><li>The environment selects organisms with beneficial traits </li></ul><ul><li>Organisms with traits well suited to the environment survive and reproduce in greater numbers than those less well suited. </li></ul><ul><ul><li>They pass these traits to their offspring </li></ul></ul>
  11. 11. Adaptation & Natural Selection <ul><li>Over time the population becomes better adapted to the environment </li></ul><ul><li>The environment does the selecting </li></ul><ul><ul><li>therefore natural selection , </li></ul></ul><ul><ul><li>artificial selection was well known </li></ul></ul><ul><ul><li>also survival of the fittest </li></ul></ul>
  12. 12. Artificial Selection Members of the cabbage family bred from wild mustard plants.
  13. 13. Key Points <ul><li>Evolution is not the same as natural selection </li></ul><ul><li>Evolution occurs in populations , not individuals! </li></ul><ul><ul><li>Population = a group of interbreeding individuals belonging to a particular species & haring a common geographical area </li></ul></ul><ul><li>Variations in the population occur randomly </li></ul><ul><li>Natural selection acts on this random variation </li></ul><ul><ul><li>This contrasts to Lamarck’s idea that variation occurs because of a change in the environment </li></ul></ul>
  14. 14. Random Variation
  15. 15. Natural Selection <ul><li>The mechanism of evolutionary change </li></ul><ul><li>Definition = selection by the environment </li></ul><ul><li>Misleading idea of an elimination contest favoring the strong and eliminating the weak </li></ul><ul><li>Darwin did not know about genetics </li></ul><ul><ul><li>Makes mechanism clear </li></ul></ul><ul><li>Sometimes misapplied or misunderstood </li></ul><ul><ul><li>Herbert Spencer </li></ul></ul><ul><ul><li>Extended to human affairs, politics: social Darwinism </li></ul></ul>
  16. 16. The Peppered Moth Example <ul><li>In England before the industrial revolution moth’s were mostly light colored </li></ul><ul><li>They lived on light colored trees </li></ul><ul><ul><li>blended with bark </li></ul></ul><ul><ul><li>hard for predators to see </li></ul></ul><ul><li>The industrial revolution led to pollution </li></ul><ul><ul><li>tree bark became darker </li></ul></ul><ul><ul><li>light moths were easy targets for predators </li></ul></ul><ul><ul><li>this favored dark moths </li></ul></ul><ul><li>NOTE: </li></ul><ul><ul><li>had to have variation in the population in the 1st place to produce dark moths! </li></ul></ul><ul><li>Recent pollution control </li></ul><ul><ul><li>return of light moths </li></ul></ul>
  17. 17. <ul><li>The Peppered Moth </li></ul><ul><li>Camouflage produces a selective advantage </li></ul><ul><li>Changing environmental conditions produce direct evidence of evolution </li></ul>
  18. 18. Evidence of Evolution <ul><li>Fossil Record </li></ul><ul><li>Comparative Anatomy </li></ul><ul><ul><li>Homologous Structures </li></ul></ul><ul><ul><li>Vestigial Structures </li></ul></ul><ul><li>Comparative Embryology </li></ul><ul><li>Biogeography </li></ul><ul><ul><li>Adaptive Radiation </li></ul></ul><ul><ul><li>Convergent & Divergent Evolution </li></ul></ul><ul><li>Direct observation of natural selection </li></ul><ul><li>Molecular Biology </li></ul>
  19. 19. The Fossil Record <ul><li>Paleontology = the study of fossils </li></ul><ul><ul><li>A record of change over time </li></ul></ul><ul><li>Sedimentary impressions </li></ul><ul><ul><li>layers = strata </li></ul></ul><ul><ul><li>allow dating </li></ul></ul><ul><li>Most are skeletal remains </li></ul><ul><ul><li>Also bogs, amber, ice </li></ul></ul><ul><li>Two theories about how changes occurred and why there are gaps: </li></ul><ul><ul><li>Catastrophism: </li></ul></ul><ul><ul><li>boundaries between strata corresponded to catastrophic events </li></ul></ul><ul><ul><li>Gradualism : </li></ul></ul><ul><ul><li>profound change is the result of slow, continual process </li></ul></ul>
  20. 20. Fossil Formation
  21. 21. Fossils (Continued) <ul><li>Study the relationship of fossils to existing organisms </li></ul><ul><ul><li>Look for similarities & differences </li></ul></ul><ul><li>Study order of fossils </li></ul><ul><li>Chronology of appearance of different classes of vertebrates: </li></ul><ul><ul><li>fishes predate other vertebrates, then amphibians, reptiles </li></ul></ul><ul><ul><li>The oldest fossils are prokaryotes </li></ul></ul><ul><ul><li>corroborates biochemical & molecular evidence </li></ul></ul><ul><li>The fossil record is incomplete </li></ul>
  22. 22. Rock Strata & Fossil Dating The Grand Canyon
  23. 23. Comparative Anatomy <ul><li>Homologous Structures </li></ul><ul><ul><li>Anatomically similar structures serve different functions in different organisms </li></ul></ul><ul><ul><li>Forelimbs of bird, horse dog have different functions yet have common internal bone structure (bat's wing, whale's flipper, homologous) </li></ul></ul><ul><li>Vestigial organs or structures </li></ul><ul><ul><li>parts that are incomplete or have no apparent function; the remains of once functioning structures. </li></ul></ul><ul><li>Evidence for common ancestry </li></ul>
  24. 24. Homologous Structures
  25. 25. Vestigial Structures
  26. 26. Embryology <ul><li>Ontogeny recapitulates phylogeny </li></ul><ul><li>Developing organism = embryo </li></ul><ul><li>The early stage of one organism is very similar to other organisms </li></ul><ul><li>Similar developmental stages may reflect common ancestry </li></ul>
  27. 27. Comparative Embryology
  28. 28. Biogeography <ul><li>The study of the distribution of plants and animals </li></ul><ul><li>Places with similar climate don't always have the same animals </li></ul><ul><li>Animals on islands may be more like those on the nearest mainland than those on islands with similar habitats elsewhere </li></ul><ul><li>Convergent Evolution </li></ul><ul><ul><li>Similar environmental pressure may produce very similar organisms which are actually not closely related </li></ul></ul><ul><li>Divergent Evolution </li></ul><ul><ul><li>Organisms that are similar may grow farther and farther apart due to different selective pressures in different environments </li></ul></ul><ul><li>Adaptive Radiation </li></ul><ul><ul><li>A type of divergent evolution  </li></ul></ul>
  29. 29. Convergent Evolution <ul><li>Natural selection favors similar organism in similar environments because they are acted on by similar pressures </li></ul><ul><li>Two organisms in similar environments may appear very similar but may be genetically very different </li></ul><ul><ul><li>fishes & dolphins; S. American rhea & African ostrich </li></ul></ul>
  30. 30. Convergent Evolution Illustrated
  31. 31. Divergent Evolution <ul><li>The process by which related organisms become less alike </li></ul><ul><li>Caused by different selective pressures in their environments </li></ul>
  32. 32. Adaptive Radiation <ul><li>One type of Divergent Evolution) </li></ul><ul><li>Many new species can arise from a single parent species </li></ul><ul><li>Darwin's finches = classic example </li></ul><ul><ul><li>On the Galapagos Islands </li></ul></ul><ul><ul><li>similar in appearance, but each species has distinctive shaped beak </li></ul></ul><ul><ul><li>distinct feeding habits and behaviors </li></ul></ul><ul><ul><li>On the Galapagos Islands, many different food sources, </li></ul></ul><ul><ul><li>evolved into different species to fill different niches </li></ul></ul><ul><ul><li>All are closely related </li></ul></ul><ul><ul><li>Arose from a single type of finch in S. America </li></ul></ul>
  33. 33. Darwin’s Finches
  34. 34. Direct Observation <ul><li>Usually difficult because of the time involved for natural selection to take place </li></ul><ul><li>Recall the peppered moth </li></ul><ul><li>Other examples: </li></ul><ul><ul><li>bacterial drug resistance </li></ul></ul><ul><ul><li>pesticide resistance in insects </li></ul></ul><ul><ul><li>drosophila </li></ul></ul>
  35. 35. <ul><li>Direct Observation </li></ul><ul><li>of Natural Selection </li></ul><ul><li>Insecticide resistance in beetles </li></ul>
  36. 36. Molecular Biology <ul><li>Includes biochemistry, molecular biology, genetics </li></ul><ul><ul><li>serum proteins in blood </li></ul></ul><ul><ul><li>amino acid sequences in proteins </li></ul></ul><ul><ul><li>proteins with similar amino acid sequence in related organisms </li></ul></ul><ul><ul><li>DNA sequencing </li></ul></ul><ul><li>Darwin did not know about genetics </li></ul><ul><ul><li>Mendel existed but there is no evidence that Darwin had read or understood Mendel's ideas </li></ul></ul><ul><li>Modern technology gives a much deeper understanding of the basis for Darwin's theory </li></ul><ul><li>In a changing environment, natural selection alters gene frequencies </li></ul>