1114 Chapter 7

  1. Frequency Dependent Selection
    The fitness of a phenotype depends on how common it is in the population
  2. Based on the graph, predict the frequency of left-mouthed individuals in the next census.



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    A) Left-mouthed individuals will decrease in frequency

    • Left- vs. Right- mouthed frequency fluctuates.
    • This is because the most common phenotype frequency hits tipping point where it is no longer most successful
  3. Coevolution
    The joint evolution of two or more interacting species in which pressure from each species acts as a selective agent on the other
  4. What type of selection is speed an example of?
    • Speed is under strong directional selection pressure in the cheetah population and the gazelle populations
    • Slow gazelles were more likely to get eaten = lower relative fitness
    • Slow cheetahs are less likely to eat = lower relative fitness
    • Cheetahs and gazelles exert selective pressures on each other
  5. What conditions would be necessary for two or more populations to coevolve?
    • Geographical overlap of the species
    • Reciprocal effects on phenotypic traits as a result of differential survival/reproduction
  6. What does reciprocal mean in reciprocal effects on phenotypic traits?
    • Each species acts as a selective pressure on the phenotype of the others (fast gazelles = selective pressure on cheetahs to be fast and vice versa)
    • Effects on fitness: A given phenotype of species A is more fit in the presence of species B
  7. Which of the following best describes the results presented?
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    C)  Where squirrels are present, pinecones are rounder and have fewer seeds/cone
  8. Which of the following best describes the results presented?
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    A) Squirrels that live with pines have larger jaw muscles than those that live without pines, on average
  9. Which of the following best describes the results presented?





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    D) 2 of the above are correct
  10. Which of the following best describes the results presented?






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    E) Two of the above are correct
  11. Based on the data presented __________ are in a coevolutionary relationship.




    D) Crossbills and pines
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1114 Chapter 7
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