Chapter 15.txt

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Chapter 15.txt
2013-07-22 19:49:17
Chapter 15

Chapter 15
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  1. What does it mean to evolve?
    To change over time.
  2. In what ways is evolutionary change observed?
    Fossils, lab experiments, natural populations.
  3. What are 5 reasons to care about evolution?
    Study and treat diseases; agri/industri applications; implications for conservation; diversification of life
  4. What is a theory?
    In everyday speech, a theory is an Untested hypothesis or a guess.
  5. What is an evolutionary theory IN SCIENCE?
    It is not a single hypothesis, but it encompasses a large body of work.
  6. What does evolutionary theory refer to?
    It refers to our understanding of the mechanisms that result in genetic changes in populations over time.
  7. What does the understanding from evolutionary theory help us do? Interpret changes of living organisms over time.
  8. Before Darwin, what was missing from biologists' suggestion that species changed over time?
  9. What did Jean-Baptiste Lamarck propose?
    He proposed the mechanism of evolution by Inheritance of Acquired characteristics in 1809.
  10. What two works influenced Darwin?
    Lyell's 'Principles of Geology' and Malthus' 'an essay on the principle of population'
  11. Which piece of work focused on Geologic Uniformitarianism?
    Principles of Geology by Lyell's
  12. Which piece focused on Populations that have potential for rapid increase but are kept in check by limited resources?
    An essay on the principle of Population by Malthus
  13. What did many of Darwin's observations come from?
    The artificial selection of domesticated plants and animals. Variants selected by breeders.
  14. How did artificial selection affect Darwin?
    He realized the same could happen in wild populations
  15. What are the 4 conditions for Natural Selection to occur?
    Variation, Heritability, more born than reproduce, variation must affect reproductive success of individuals
  16. What is important misconception #1 in regards to evolution?
    Evolution doe NOT equal natural selection
  17. What is natural selection?
    A mechanism by which evolution can occur
  18. What is the important misconception #1 in regards to evolution?
    Evolution happens to POPULATIONS, not to individuals.
  19. How do genotypes and phenotypes apply to individuals and populations?
    INDIVIDUALS have phenotypes and genotypes while populations have DISTRIBUTIONS of phenotypes, genotypes, and alleles.
  20. What is a frequency?
    It is a characterization of distribution. (#/TOTAL).
  21. How is the genotype frequency calculated?
    (# of INDIVIDUALS with genotype in population/ TOTAL # of individuals in population)
  22. How is allele frequency calculated?
    (# copies of allele in population/TOTAL # of copies of all alleles in population)
  23. How do you calculate the frequency of Genotype XX?
    N(XX) / N
  24. What is the formula for allele frequency of p (A) and q (a)?
    ( 2N(AA) + N(aa) ) / 2N = p while ( 2N(aa) + N(Aa) ) / 2N = q
  25. What is p + q?
    It is a frequency. It will always equal 1.
  26. How can evolution be measured?
    By changes in allele frequencies
  27. What are two notes Darwin made?
    More individuals are born than survive to reproduce; offspring look like parents but aren't identical
  28. What was one of darwin's conclusions?
    Differences among individuals affect chances to survive & reproduce, this will increase freq of beneficial traits in next generation
  29. What are the 3 things that must be in line for natural selection to occur?
    Variation, heritability, and some variants must be better able to survive and/or reproduce than other (fitness)
  30. What is adaptation?
    A trait that is favorable in current environment and evolves through natural selection.
  31. What describes the process that produces the trait?
  32. What happens to the frequency if a population has variation in a trait?
    There will be an increase in the frequency of that trait in the next generation
  33. What is the origin of genetic variation?
  34. What is mutation?
    Any change in nucleotide sequences
  35. What are the 3 types of mutations?
    Deleterious, beneficial, or neutral
  36. What is the process that occurs between mutation and adaptation?
    Mutations occur randomly with respect to an organism's needs, natural selection then acts on this new random variation which results in adaptation
  37. Does natural selection always result in the best possible phenotype?
  38. What happens to frequency if a variation is heritable.
    There will be an increase in frequency of that trait in the next generation
  39. What is heritability and what is the formula?
    Heritability is the proportion of total phenotypic variation that is due to genetic variation (h^2) = Vg / Vp
  40. How is heritability measured?
    By the slope of a parent-offspring regression
  41. What happens to frequency if some variants are better able to survive and/or reproduce than others (i.e. have higher fitness)?
    There will be an increase in the frequency of that trait in the next generation
  42. What is fitness?
    The contribution of a genotype of phenotype to the genetic composition of subsequent generations, relative to the contribution of other genotypes or phenotypes.
  43. What is directional selection?
    Individuals at one extreme of a character distribution contribute more offspring to the next generation.
  44. What is a stabilizing selection?
    It is when the mean phenotype has the highest fitness and individuals with extreme phenotypes have the lowest fitness
  45. How does stabilizing selection affect variation and mean?
    It reduces variation, but does NOT change the mean.
  46. What is disruptive selection?
    It is when individuals at opposite extremes of a character distribution contribute more offspring to the next generation.
  47. How does disruptive selection affect variation?
    It increases variation in populations and can result in bimodal distribution of traits.
  48. What is frequency dependent selection?
    It is a type of selection where the fitness of a phenotype varies depending on how common that phenotype is
  49. What are the two different kinds of frequency dependent selection?
    Positive (common phenotypes favored), and negative (rare phenotypes favored)
  50. Describe positive frequency-dependent selection.
    Most common has advantage, can lead to quicker fixation of common phenotype
  51. Describe negative frequency dependent selection.
    Rare have advantage, leads to maintenance of polymorphism over time.
  52. What is sexual selection?
    A specific type of selection in which organism's phenotype influences changes of mating and thus reproduction
  53. What are two types of sexual selection?
    Male competition, or female choice.
  54. What is Male competition?
    When males compete for access to mates (intrasexual selection).
  55. What is female choice in regards to sexual selection?
    The female chooses which male phenotype she likes best (intersexual selection)
  56. What are some examples of intrasexual selection?
    Direct combat or ritualized fighting between males, also mate guarding and sneaker males
  57. What is mate guarding
    When a male prevents access to female by other males
  58. What is a sneaker male
    A male that prevents the success of successful males.
  59. Tell me about intersexual selection:
    Males may provide a direct benefit to females, thus allowing them to produce more offspring; females may be selecting for traits that indicate health or longevity. "good genes" to pass off to their offspring. Traits may be sensory bias
  60. What is sensory bias
    When the traits that are chosen may be arbitrary & unrelated to male quality.
  61. How do males and females differ in investment reproductively?
    Females have greater investment, starting at the size of gamete level.
  62. What is anisogamy
    Unequal sized gametes
  63. What does the difference in reproductive investment between males and females suggest?
    Females should be more choosy, males can monopolize the reproduction of multiple females.
  64. What is population genetics?
    Study of allele frequency distributions and their change over time in response to various evolutionary forces
  65. At what frequency will gametes be produced?
    Gametes will be produced at the same frequency as allele frequency within the population's gene pool
  66. What is the formula for total genotype frequency?
    p^2 + 2pq + q^2 = 1
  67. What does Hardy-Weinberg equilibrium suggest?
    It suggests that allele frequencies do not change across generations.
  68. What are the 5 assumptions for Hardy-Weinberg equilibrium?
    No mutation, No selection, Random mating, Infinite population size ( no genetic drift), no gene flow (i.e. no forces of evolution are acting)
  69. How are allele frequencies acting at Hardy-Weinberg?
    The frequencies of alleles do no change
  70. What is interesting about population in nature in regards to HWE?
    Populations in nature NEVER meet the conditions of the equilibrium because all biological populations evolve.
  71. What is selection?
    An increase in the next generation in the frequency of traits that increase survival or reproduction
  72. What is the heterozygous advantage?
    When heterozygotes are advantageous in variable environmental conditions, polymorphic loci are likely to be maintained
  73. What type of selection changes allele frequencies across generations?
  74. What type of mating changes genotype frequencies out of HW eq?
    Assortive. Selfing, or self-fertilization, is common in plants and other forms of assortive mating.
  75. What happens to genotype frequencies in assortative mating?
    Homozygous genotypes increase in f and heterozygous genotypes will decrease.
  76. What is genetic drift?
    When random changes in allele frequencies from one generation to the next, due to random variation in survival, reproduction, and gamete sampling.
  77. What does genetic drift eliminate? What can it result in?
    It eliminates genetic variation and can result in fixation.
  78. What is fixation?
    It occurs when one allele is lost and the other is the only one present in the population .
  79. Which populations does genetic drift have a bigger effect on?
    Genetic drift has a bigger effect on allele frequencies in small populations, larger populations take longer for allele to drift to fixation
  80. What is population bottleneck?
    When an environmental event results in survival of only a few individuals.
  81. What happens to the variation of populations that undergo bottnecks?
    They lose much of the genetic variation due to random sampling and an increased effect of genetic drift.
  82. What dis migration of individuals between populations result in?
    Gene flow; which can change allele frequencies
  83. What does the effect that gene flow has depend on, in regards to migration?
    Number of migrants and the size of population
  84. What is the founder effect?
    When a few individuals from a population start a new population with a different allele frequency than the original (migration + bottleneck)
  85. How do mutations affect allele frequencies?
    mutations can create deleterious alleles faster than selection can remove them
  86. In what ways can drift affect a beneficial allele?
    It can cause the loss of the allele in a small population, even though it is favored by selection
  87. Which evolutionary processes can reduce varation and lead to fixation?
    Selection and drift
  88. What processes can create or maintain variation in a population?
    Mutation, migration, disruptive or negative frequency-dependent selection, heterozygote advantage.
  89. Synonymous substitutions and how they affect phenotype.
    They don't affect phenotype because most amino acids are specified by more than one codon.. (silent mutation)
  90. Nonsynonimous substitutions and amino acid effects?
    (missense, frameshift, or nonsense mutations); changes one or more amino acid in the sequence
  91. Which substitutions persist in populations?
    The ones that are at positions that don't change amino acid being expressed
  92. What are pseudogenes?
    Copies of genes that are no longer functional
  93. Where are substitutions the highest?
    In pesudogenes
  94. What is natural theory?
    At the molecular level, the majority of variants in most populations are selectively neutral.
  95. How must neutral variants accumulate?
    Through genetic drift rather than positive selection.
  96. Rate of fixation of new neutral mutations by genetic drift are independent of what?
    Population size.
  97. What is a molecular clock?
    A rate of mutation of particular genes and proteins which are often relatively constant over time. Can be used to calculate evolutionary divergence times between species.
  98. What is the result of more fixed neutral mutations?
    More time elapsed

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