Review organic evolution


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Quick review of concepts of organic evolution

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Review organic evolution

  1. 1. A Quick Review ofEvolution<br />
  2. 2. Evolution<br />Evolution is the central theme of biology<br />Nothing in biology makes sense except in the light of evolution<br />Theodosius Dobzhansky <br />
  3. 3. Evolution<br />Evolution: change over time; can be applied to many things, so we use a more specific definition in biology<br />Organic evolution = change in allele frequencies over time<br />Allele = alternate form of a gene; if one variation of a gene confers some sort of advantage in a particular environment, it is more likely to be passed on.<br />
  4. 4. Evolution<br />The term evolution does not imply a mechanism<br />many mechanisms have been hypothesized<br />Natural Selection is accepted as the primary mechanism of adaptive evolution<br />Other mechanisms include sexual selection, genetic drift, and genetic bottlenecks.<br />How does evolution occur?<br />
  5. 5. Speciation<br />Speciation: the formation of a new species<br />can proceed by many mechanisms<br />results in the bifurcation(separation of 1 into 2) of a lineage(group of related organisms)<br />
  6. 6. Speciation<br />Allopatric Speciation: believed the most common method of speciation (and the method of human speciation). <br />Results primarily from genetic drift and Natural selection<br />
  7. 7. Genetic Drift<br />Genetic Drift: random change in allele frequencies over time<br />most common in genes not subject to natural selection<br />Differences accumulate when two populations become separated from each other.<br />
  8. 8. History of Evolution<br />Evolution is an old theory<br />Darwin didn’t come up with evolution<br />He did provide evidence for it and therefore popularized it and made possible the scientific discipline called evolutionary biology.<br />He also didn’t come up with the phrase “survival of the fittest” that you should probably forget you ever heard.<br />
  9. 9. Darwin<br />Charles Darwin used and preferred the phrasedescent with modification<br />Darwin developed the theory of Natural Selection<br />It is a mechanism of evolution, not an equivalent term to evolution<br />Who came up with the idea of natural selection independent of Darwin?<br />Alfred RusselWallace<br />Known as the father of biogeography<br />
  10. 10. Influences<br />Charles Lyell<br />Popularized uniformitarianism, a concept developed by James Hutton.<br />Thomas Malthus<br />Wrote an essay on population that highlighted a struggle for limited resources in a large population.<br />
  11. 11. Inspiration - Geology<br />Uniformitarianism:the processes which shape the earth today are the sameandoccur at the same ratesas the processes that have shaped the earth in the past<br />For example, canyons formed over a very long time through the same process of erosion as occurs right now; sand on the beach formed through millenia of waves hitting the shore just like they do now.<br />
  12. 12. Natural Selection - Logical Argument<br />1Reproduction results in more offspring than the size of the current population<br />2 There is variationin all traits (phenotype)<br />3 Much of the variation is heritable<br />4There is variation in fitness as a result of having or not having certain variations of traits.<br />
  13. 13. Fitness<br />Fitness: average number of offspring left by an individual relative to the number of offspring left by an average member of the population<br />You could say Fitness = Relative Reproduction<br />What can influence fitness?<br />
  14. 14. Natural Selection<br />If natural selection occurs:<br />the distribution of genotypes (phenotypes) of the next generation will reflect the distribution of the more fit members of the previous generation<br />Not all traits are under the influence of natural selection<br />
  15. 15. What happens depends on the nature of the selective force: It is not progressive, it depends on the environmentWhy do some find this idea so disturbing?<br />
  16. 16. Forms of Selection<br />Stabilizing selection<br />Directional selection<br />Disruptive selection<br />
  17. 17. Definitions<br />Mutation: any change occurring in the message that a gene carries <br />Provides variation upon which natural selection can act<br />Usually the result of copy errors during DNA replication in mitosis or meiosis<br />
  18. 18. Definitions<br />Adaptation: the condition of organisms being<br />well fit for life in their environments<br />as resulting from natural selection<br />Non-adaptive change?<br />Acclimation<br />
  19. 19. Definitions<br />Exaptation: a biological trait (adaptation) where the current biological function is different from the function of the original adaptation<br />Or, you could say<br />The selection pressures are now exerted on a different function than those that initially controlled the trait<br />
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  21. 21. Definitions<br />Phenotypic plasticity: sometimes the same genotype is expressed as a different phenotype in different environments<br />The organism has not adapted<br />Acclimation<br />
  22. 22. Units of Evolution and Natural Selection<br />Unit of evolution=Species<br />can change over time based on the differential representation of genes in each generation caused by natural selection <br />It is often more proper to view the population as the unit of evolution<br />When are a species and population not equivalent?<br />
  23. 23. Units of Evolution and Natural Selection<br />Unit of selection=An individual<br />the unit that survives or does not, breeds or does not, passes on genes to the next generation or does not<br />Individuals do not evolve<br />
  24. 24. How does Evolution Illustrate the History of Life?<br />Phylogeny: branching diagram indicating the evolutionary history of an organism<br />What does the history of life look like?<br />A phylogeny is a data based hypothesis about evolutionary relationships<br />How is it a hypothesis?<br />
  25. 25. Phylogeny<br />What kind of information is used to make a phylogeny?<br />Derived Homologies<br />What are homologies?<br />What does derived mean?<br />
  26. 26. Phylogeny<br />Analogous: shared by 2 or more species, but not present in their common ancestor<br />Likely developed by convergent evolution<br />Homologous: shared by 2 or more species, also present in their common ancestor<br />
  27. 27.
  28. 28. Phylogeny<br />Ancestral homologies: present in common ancestor and more distant relatives<br />Opposable thumb in apes<br />Derived homologies: evolved in common ancestor, not present in more distant ancestors<br />Opposable thumb in primates<br />
  29. 29. What types of data support evolution?<br />Stephen J. Gould discusses three arguments for evolution in his essay “Evolution as Fact and Theory” <br />
  30. 30. Direct observational evidence<br />
  31. 31. Imperfections of nature<br />Why?<br />Conflicts between selection pressures and limitations of descent<br />Humans:<br />increased brain size<br />requires large pelvic outlet<br />bipedal locomotion<br />requires narrow pelvic outlet<br />
  32. 32. Transition fossils<br />