Exam (elaborations)
BIO 182 Exam 2 Questions and answers latest update 2024
- Course
- BIO 182
- Institution
- Arizona State University
BIO 182 Exam 2 Questions and answers latest update 2024
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BIO 182 Exam 2 b b b1. How many modes of selection are there?: 3
b b b b b b b
2. What are the modes of selection?: Stabilizing selection, directional selection,
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b and disruptive selection
b b
ime but b
3. Stabilizing Selection: The mean of the trait remains similar over t b b b b b b b b b b
b standard deviation decreases b b
4. Directional Selection: The mean phenotype shifts in a particular b b b b b b b b directio
5. Disruptive Selection: The standard deviation of the trait increases b b b b b b b b as
individuals
b
b with the mean value disappear.
b b b b
6. Stabilizing Selection Explained: The stronger the selective pressure against
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b extreme phenotypes, the narrower the distribution of phenotypes will be in future
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b generations. In the end, the size of the standard deviation will reflect both the
b b b b b b b b b b b b b
b strength of selection against extremes and the frequency of mutations creating new
b b b b b b b b b b b
b variation. Thus, when we observe a wide range of phenotypes in a population, we
b b b b b b b b b b b b b
b might infer weak selective pressure against the extremes.
b b b b b b b
7. Directional Selection Explained: The population's environment changes. The b b b b b b b
b mean phenotype in the population may no longer be the phenotype that reproduces
b b b b b b b b b b b b
b the most. Over time, we should expect the mean phenotype to shift higher or lower,
b b b b b b b b b b b b b b
b depending on the direction of selective pressure. Once the mean phenotype catches
b b b b b b b b b b b
b up to the change in the environment, stabilizing selection will resume.
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The environment must change slowly enough for the population to persist. If the
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b environment changes too quickly, no members of the population will be able to
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b b
, BIO 182 Exam 2 b b b
b reproduce, leading to extinction.
b b b
8. Disruptive Selection Explained: A population can occupy an environment in
b b b b b b b b b
b which individuals with extreme phenotypes reproduce more than individuals with
b b b b b b b b b
b the mean phenotype.
b b
This mode of selection occurs when several distinct strategies confer greater
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b reproductive success than other strategies do. Can produce new species when
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b individuals choose to mate only with similar-looking individuals. This non-random
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b mating prevents recombination from restoring intermediate phenotypes.
b b b b b b
9. Evolution by Natural Selection: Heritable variation leads to differential repro-
b b b b b b b b b
b ductive success b
10. Selection and Fitness: b b
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b b
, BIO 182 Exam 2 b b b
11.Directional Selection Equation: y=bx+c b b b
y=relative fitness b
b x= trait value
b b
b= strength of selection
b b b
b c=parameter
12.True or False? If the slope of the relationship between the phenotype and
b b b b b b b b b b b b
b fitness is positive, natural selection would decrease the phenotype over
b b b b b b b b b
b generations.: False, it would increase the value of the trait over time
b b b b b b b b b b b
13.Stabilizing Selection Equation: y=ax^2+bx+c b b b
y=relative fitness b
b x= trait value
b b
a/b= strength of selection
b b b
b c= parameter
b
14.True or False? If the parameter for the squared term is negative, natural
b b b b b b b b b b b b
b selection will likely stabilize the phenotype at an intermediate value.: True,
b b b b b b b b b b
b depends on how large the parameter is for the squared term
b b b b b b b b b b
15.What is fitness?: The relative number of viable, fertile offspring
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16.What does natural selection do?: Natural selection not only changes mean
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b phenotypes but also increases or decreases deviations from mean phenotypes.
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17.What type of selection is most common?: All three can happen to some extent.
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b b
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