AP Evolution Notes

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Rough draft of Notes on evolution theories and concepts for AP Biology. Utilizing Campbell, Reece., Mitchell, Biology 4th Ed.

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AP Evolution Notes

  1. 1. Evolution - A change in a population over time. Chapters 22-24
  2. 2. <ul><li>Pre-Darwin Theories: </li></ul><ul><li>1. “Idealism” (Essentialism) -States that there are 2 worlds: an ideal, real world and an illusionary world the humans perceive w/ senses. </li></ul><ul><ul><li>Variations in plants & animals were imperfect representations of ideal forms. </li></ul></ul><ul><ul><li>Evolution is counterproductive since ideal organisms are already perfectly adapted to environments. </li></ul></ul><ul><li>(Plato - who disagreed w/ gradual evolution) </li></ul>
  3. 3. <ul><li>Pre-Darwin Theories (Continued): </li></ul><ul><li>2. “Scala Natura” - Stated that organisms vary from simple to complex and that species are fixed and do not evolve. Prevailed for over 2000 years. </li></ul><ul><li>(Aristotle - Questioned Plato but excluded evolution) </li></ul>
  4. 4. <ul><li>Pre-Darwin Theories (Continued): </li></ul><ul><li>3. “Creationist - essentialist” - Based on the Old Testament account that species were individually created and fixed. Embedded in Western / Judeo-Christian culture. Fortified prejudice against evolution. </li></ul><ul><ul><li>“ Natural Theology” - the philosophy that the Creator’s plan could be revealed by studying nature. </li></ul></ul><ul><ul><li>Adaptations were thought of as being created for specific purposes. </li></ul></ul>
  5. 5. <ul><li>Pre-Darwin Theories (Continued): </li></ul><ul><li>4. “Taxonomy” - Grouped organisms by categories and ranked categories by similarity. This lead to “binomial nomenclature” still used today. </li></ul><ul><ul><li>Clustering species into groups did not imply evolutionary relationships since he believed species were permanent fixtures. </li></ul></ul><ul><ul><li>Was done only to reveal “God’s” plan. </li></ul></ul><ul><li>(Linneaus, 1707 - 1778, “Natural Theologian” - sought to order the diversity of life “for the greator glory of the creator”) </li></ul>
  6. 6. Charles Darwin <ul><li>Published the 1st convincing case for evolution in a book “On the Origin of Species by Means of Natural Selection” in 1859 based on his voyage on the HMS Beagle. </li></ul>
  7. 7. <ul><li>Darwin (Continued): </li></ul><ul><li>The book: </li></ul><ul><li>Synthesized seemingly unrelated facts to create a conceptual framework that accounts for both the unity & diversity of life. </li></ul><ul><li>Discussed important biological issues about organisms, such as why there are so many different kinds of organisms, their organs and relationships, similarities & differences, geographic distribution, & adaptations to their environment. </li></ul>
  8. 8. <ul><li>Darwin (Continued): </li></ul><ul><li>The book made 2 major points: </li></ul><ul><ul><li>Species evolved from ancestral species & were not specially created. </li></ul></ul><ul><ul><li>“ Natural selection” is a mechanism that could result in this evolutionary change. </li></ul></ul>
  9. 9. <ul><li>Natural Selection - &quot;The survival of the fittest&quot; the first proposed explanation of variation of life on Earth. It is now considered the mechanism of evolution. It states that survival is based on fitness of the organism. </li></ul><ul><ul><li>Fit is now defined as best able to pass on genetic material to offspring. </li></ul></ul>(Charles Darwin, 19th century)
  10. 10. <ul><li>Types of Natural Selection : </li></ul><ul><li> 1. Directional - One phenotype is favored in the </li></ul><ul><ul><ul><li>environment. </li></ul></ul></ul><ul><ul><ul><li>(ex. &quot;dark&quot; peppered moths have higher survival rates in soot covered forests) </li></ul></ul></ul><ul><ul><li>2. Stabilizing - Organisms with extreme phenotypes are </li></ul></ul><ul><ul><ul><li>eliminated. </li></ul></ul></ul><ul><ul><ul><li>(ex. birth weight in humans, low survival rate for extremes) </li></ul></ul></ul><ul><li> 3. Disruptive - Organisms with common traits are </li></ul><ul><ul><ul><li>eliminated, extremes are favored. </li></ul></ul></ul><ul><ul><ul><li>(ex. small female and large male elephant seals) </li></ul></ul></ul><ul><li> 4. Artificial - A breeder chooses which traits to favor. </li></ul><ul><li> (ex. seedless grapes) </li></ul>
  11. 11. <ul><li>Types of Evolution: </li></ul><ul><li>1. Divergent - Closely related species have different </li></ul><ul><ul><ul><li>behaviors and traits. (ex. Color variations in peppered </li></ul></ul></ul><ul><ul><ul><li>moths or beak types in finches) </li></ul></ul></ul><ul><li>2. Convergent - Unrelated species come to have similar </li></ul><ul><ul><li>traits. (ex. aardvarks, anteaters, and pangolins all have sharp teeth and claws, long snouts, and sticky tongues but evolved from 3 different mammals) </li></ul></ul>
  12. 12. <ul><li>Fossil - Based Theories: </li></ul><ul><li>1. “Catastrophism” - The theory that major changes in the Earth’s crust are the result of catastrophic events rather than gradual change. This was the first to mention extinction. </li></ul><ul><ul><li>Differences between fossil strata correspond to catastrophic events </li></ul></ul><ul><ul><li>New species in younger rocks explained by periodic local catastrophies. Foreign species would replace local extinct species. </li></ul></ul><ul><li>(Couvier, 1769 - 1832, Who developed “palentology” - the study of fossils). </li></ul>
  13. 13. <ul><li>Fossil - Based Theories (Continued): </li></ul><ul><li>2. “Gradualism” - Theorized profound change is the cumulative product of slow, continuous processes. This competed with catastrophism. </li></ul><ul><li>(James Hutton) </li></ul>
  14. 14. <ul><li>Fossil - Based Theories (Continued): </li></ul><ul><li>3. “Uniformitarianism” - Theorizes that geological processes are so uniform that their effects balance out over time. This was an expansion of gradualism that was rejected by Darwin but influential to him. </li></ul><ul><li>Ex. Mountains & erosion </li></ul><ul><li>Observations: </li></ul><ul><ul><li>Slow processes can cause substantial change. </li></ul></ul><ul><ul><li>Earth is ancient if geology is a slow process. (Charles Lyell) </li></ul></ul>
  15. 15. <ul><li>Fossil - Based Theories (Continued): </li></ul><ul><li>4. &quot;The Law of Use & Disuse&quot; - states that acquired traits </li></ul><ul><li>are inheritable. Now proven incorrect - changes in </li></ul><ul><li>somatic cells are not passed on through germ cells. </li></ul><ul><li>Darwin also dismissed this theory. </li></ul><ul><li>(Jean-Baptiste de Lamarck, 18th century). </li></ul>
  16. 16. <ul><li>Modern Theories: </li></ul><ul><li>1. Punctuated Equilibrium - Long periods of stasis punctuated by episodes of relatively rapid speciation and change. </li></ul><ul><li>(In geologic time, a few thousand years for a species to evolve is small compared to the few millions of years a successful species may exist) </li></ul><ul><li>*Long periods of stasis may be the result of stabilizing selection in an unchanging environment. </li></ul>
  17. 17. <ul><li>Modern Theories (Cont’d): </li></ul><ul><li>2. Biological Species Concept - Defined species as a population or group of populations whose members have the potential to interbreed with one another in nature and produce viable, fertile offspring. </li></ul><ul><li>(Earnst Mayr, 1942) </li></ul>
  18. 18. There’s a catch to the biological species concept! <ul><li>It does not work in all situations. </li></ul><ul><li>It cannot be applied to: </li></ul><ul><li>Completely asexual organisms, ex. clones. </li></ul><ul><li>Extinct organisms represented only via fossils. </li></ul><ul><li>There are other possibilities: </li></ul><ul><li>Morphological species concept </li></ul><ul><li>Recognition species concept </li></ul><ul><li>Cohesion species concept </li></ul><ul><li>Ecological species concept </li></ul><ul><li>Evolutionary species concept </li></ul>
  19. 19. <ul><li>Speciation - The origin of new species </li></ul><ul><li>Patterns of Speciation: </li></ul><ul><li>1. Anagenesis - (phyletic evolution) Involves the transformation of an entire species into a new species. </li></ul><ul><li>2. Cladogenesis - (branching evolution) New species arise from a parent species that continue to exist. </li></ul>
  20. 20. <ul><li>Modes of Speciation: </li></ul><ul><li>Allopatric - population becomes separated from rest of </li></ul><ul><li>species by a geographic barrier. </li></ul><ul><li>Leads to: </li></ul><ul><ul><ul><li>Colonization of new areas </li></ul></ul></ul><ul><ul><ul><li>Founder effects - the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population </li></ul></ul></ul><ul><ul><ul><li>Genetic drift - the change in the relative frequency with which an allele occurs in a population that results from the fact that alleles in offspring are a random sample of those in the parents, and because of the role of chance in determining whether a given individual survives and reproduces. Genetic drift may reduce genetic variability. </li></ul></ul></ul><ul><ul><ul><li>Differing selection pressures - due to different habitats. </li></ul></ul></ul><ul><ul><ul><li>Adaptive radiation on island chains - the evolution of many adapted species from a common ancestor. </li></ul></ul></ul>
  21. 21. <ul><li>Modes of Speciation (Cont’d): </li></ul><ul><li>Sympatric - Formation of a new species without a geographic barrier. </li></ul><ul><ul><ul><li>Reproductive isolation evolves w/o geographic isolation. </li></ul></ul></ul><ul><ul><ul><li>Can occur quickly if genetic change results in reproductive barrier between mutants and parent population. </li></ul></ul></ul><ul><ul><ul><li>Varieties: </li></ul></ul></ul><ul><ul><ul><li>Autopolyploid - An organism w/ two or more complete sets of chromosome within each cell, all derived for a single species. </li></ul></ul></ul><ul><ul><ul><ul><li>Ex. 4n - Potatoes, 3n - Apples & Bananas </li></ul></ul></ul></ul><ul><ul><ul><li>Allopolyploid - n organism w/ two or more complete sets of chromosomes within each cell, derived from different species. (More common than autopolyploidy) </li></ul></ul></ul><ul><ul><ul><ul><li>Ex. 6n - Triticale, from 4n from wheat and 2n from rye </li></ul></ul></ul></ul>
  22. 22. <ul><li>Barriers isolate the gene pools of biological species </li></ul><ul><li>Types of Barriers: </li></ul><ul><li>Prezygotic (Before Fertilization): </li></ul><ul><ul><li>1. Habitat Isolation - 2 species in different habitats. </li></ul></ul><ul><ul><li>2. Behavioral Isolation - Signals/behaviors attract mates. </li></ul></ul><ul><ul><li>3. Temporal Isolation - Species breed at different times, day/season/years. </li></ul></ul><ul><ul><li>4. Mechanical Isolation - Anatomical incompatibility. </li></ul></ul><ul><ul><li>5. Gametic Isolation - Gametes of different species fail to </li></ul></ul><ul><li>attract one another. </li></ul>
  23. 23. <ul><li>Types of Barriers (Cont’d) </li></ul><ul><li>Postzygotic (After Fertilization): </li></ul><ul><ul><li>1. Reduced Hybrid viability - hybrids lack vigor and rarely, if ever, reach sexual maturity. </li></ul></ul><ul><ul><li>2. Reduced Hybrid Fertility - hybrids are usually sterile. </li></ul></ul><ul><ul><li>3. Hybrid Breakdown - hybrids can reproduce but their offspring have either reduced fertility or reduced viability. </li></ul></ul>
  24. 24. <ul><li>Evolution is not goal oriented, </li></ul><ul><li>but trends do occur… </li></ul><ul><ul><li>It is possible to isolate a single evolutionary progression. Ex. Horse evolution </li></ul></ul><ul><ul><li>Branching evolution can produce a trend even if some new species counter the trend. </li></ul></ul><ul><ul><li>Species are analogous to individuals (Steven Stanley of John’s Hopkins) </li></ul></ul><ul><ul><li>The presence of an evolutionary trend does not mean there is an intrinsic drive toward a preordained state. </li></ul></ul>
  25. 25. <ul><li>Most evolutionary novelties are modified versions of older structures </li></ul><ul><li>Exaptation - a structure that evolves in one context and becomes co-opted for another function </li></ul><ul><ul><li>Cannot be proven, but explains how novel designs can arise gradually. </li></ul></ul><ul><ul><li>Higher taxa such as families and classes are defined by evolutionary novelties (Ex. Birds are adapted to flight but ancestors are earthbound) </li></ul></ul><ul><ul><li>Natural selection can not anticipate the future, but it can improve an existing structure. </li></ul></ul><ul><ul><li>Reflects the Darwinian tradition of large changes as a result of natural selection through many small changes. </li></ul></ul>
  26. 26. <ul><li>Genes that control development play a major role in evolutionary novelties. </li></ul>
  27. 27. <ul><li>Terms to Recognize: </li></ul><ul><li>Allometric growth - Differences in relative rates of growth of various parts of the body. Ex. Human head size compared to body size, large in babies/small in adults </li></ul><ul><li>Heterochrony - Evolutionary changes in the timing or rate </li></ul><ul><li>of development. Ex. Head/brain development in humans Vs. chimps, same rate but chimp growth stops after birth,human growth continues. </li></ul><ul><li>Paedomorphosis - Retention of ancestral juvenile structures in a sexually mature adult organism. Ex. 1. Salamanders retain gills in adulthood, unlike most amphibians. 2. Docility is a juvenile behavior retained in domesticated pets. </li></ul><ul><li>Homeosis - Alteration in the placement of different body parts. Ex. Fruit fly legs develop in place of antennae. </li></ul>
  28. 28. <ul><li>Population Genetics </li></ul><ul><li>Hardy - Weinberg Law - The relative genotypes of a population remain constant over time if the following 5 conditions are met: </li></ul><ul><li>1. Large population </li></ul><ul><li>2. No mutations </li></ul><ul><li>3. No immigration or emigration </li></ul><ul><li>4. Random mating </li></ul><ul><li>5. No natural selection </li></ul>
  29. 29. Hardy-Weinberg Equations : The sum of the frequencies of each allele, dominant (p) and recessive (q), in a population add up to 1. p + q = 1 The frequency of the genotypes in a population may be determined using the following equation: p 2 + 2pq + q 2 = 1 homozygous dominants (p), heterozygotes (pq), homozygous recessives (q)

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