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BIO B182 BEXAM B2 NEWLY UPDATED QUESTIONS WITH CORRECT ANSWERS ALREADY GRADED A+
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BIO B182 BEXAM B2 NEWLY UPDATED QUESTIONS WITH CORRECT ANSWERS ALREADY GRADED A+
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BIO 182 EXAM 2 NEWLY UPDATED QUESTIONS WITH CORRECT ANSWERSB B B
ALREADY GRADED A+
1. How many modes of selection are there?: 3
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2. What are the modes of selection?: Stabilizing selection, directional selection,
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bb and disruptive selection
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ime but bb
3. Stabilizing Selection: The mean of the trait remains similar over t
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bb standard deviation decreases
bb bb
4. Directional Selection: The mean phenotype shifts in a particular directio
bb bb bb bb bb bb bb bb
5. Disruptive Selection: The standard deviation of the trait increases as
bb bb bb bb bb bb bb bb
individuals bb
with the mean value disappear.
bb bb bb bb bb
6. Stabilizing Selection Explained: The stronger the selective pressure against
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bb extreme phenotypes, the narrower the distribution of phenotypes will be in
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1 bb/
,bb future generations. In the end, the size of the standard deviation will reflect both
bb bb bb bb bb bb bb bb bb bb bb bb bb
bb the strength of selection against extremes and the frequency of mutations creating
bb bb bb bb bb bb bb bb bb bb bb
bb new variation. Thus, when we observe a wide range of phenotypes in a
bb bb bb bb bb bb bb bb bb bb bb bb
bb population, we might infer weak selective pressure against the extremes.
bb bb bb bb bb bb bb bb bb
7. Directional Selection Explained: The population's environment changes. The
bb bb bb bb bb bb bb
bb mean phenotype in the population may no longer be the phenotype that reproduces
bb bb bb bb bb bb bb bb bb bb bb bb
bb the most. Over time, we should expect the mean phenotype to shift higher or
bb bb bb bb bb bb bb bb bb bb bb bb bb
bb lower, depending on the direction of selective pressure. Once the mean phenotype
bb bb bb bb bb bb bb bb bb bb bb
bb catches up to the change in the environment, stabilizing selection will resume.
bb bb bb bb bb bb bb bb bb bb bb
The environment must change slowly enough for the population to persist. If the
bb bb bb bb bb bb bb bb bb bb bb bb
bb environment changes too quickly, no members of the population will be able to
bb bb bb bb bb bb bb bb bb bb bb bb
bb reproduce, leading to extinction. bb bb bb
8. Disruptive Selection Explained: A population can occupy an environment in
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bb which individuals with extreme phenotypes reproduce more than individuals
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bb with the mean phenotype.
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This mode of selection occurs when several distinct strategies confer greater
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bb reproductive success than other strategies do. Can produce new species when
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bb individuals choose to mate only with similar-looking individuals. This non-random
bb bb bb bb bb bb bb bb bb
bb mating prevents recombination from restoring intermediate phenotypes.
bb bb bb bb bb bb
2 bb /
,9. Evolution by Natural Selection: Heritable variation leads to differential
bb bb bb bb bb bb bb bb
bb repro- ductive success
bb bb
10. Selection and Fitness:
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3 /
bb
, 11.Directional Selection Equation: y=bx+c bb bb bb
y=relative fitness bb
bb x= trait value
bb bb
b= strength of selection
bb bb bb
bb c=parameter
12.True or False? If the slope of the relationship between the phenotype
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bb and fitness is positive, natural selection would decrease the phenotype over
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bb generations.: False, it would increase the value of the trait over time
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13.Stabilizing Selection Equation: y=ax^2+bx+c bb bb bb
y=relative fitness bb
bb x= trait value
bb bb
a/b= strength of bb bb
bb selection c= parameter
bb bb
14.True or False? If the parameter for the squared term is negative,
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4 /
bb
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