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ALL answers must come from your text on pages 310 to 313. Googled answers will be marked wrong.
MAIN IDEA: Natural selection acts on distributions of
traits.
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1.
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What is a phenotypic distribution?
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2.
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What can you learn from looking at a phenotypic distribution?
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3.
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In a population that is not undergoing natural selection for a certain trait,
what does the phenotypic distribution look like?
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4.
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In the space provided below, describe the phenotypic distribution for a trait
that follows a normal distribution. Be sure to explain in detail the location of the axes and
describe the mean phenotype.
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5.
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List three (3) other types of data might follow a normal distribution.
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MAIN IDEA: Natural selection
can change the distribution of a trait in one of three ways.
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6.
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Describe directional selection.
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7.
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Describe stabilizing selection.
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8.
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Describe disruptive selection.
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9.
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Refer to Figure 2.5 on page 313: If bluish brown coloring became advantageous
for young males, what type of selection would likely occur in a lazuli bunting population?
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VOCABULARY
CHECK
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10.
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The observable change in _____________ over time is called
microevolution.
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11.
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During ______________ selection, the intermediate phenotype is selected
for.
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12.
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During ______________ selection, both extreme phenotypes are selected
for.
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13.
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During ______________ selection, the mean phenotype changes.
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Formative Assessment 11.2:
Answer in complete sentence(s).
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14.
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In terms of phenotypes, describe what is meant by the phrase
“distribution of traits.”
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15.
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What are the three (3) ways in which natural selection can change a distribution
of traits?
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16.
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Predict. How might the extinction of downy woodpeckers affect the
phenotypic distribution of gall flies?
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17.
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Predict. How might overfishingof large pink salmon select for smaller
body size in subsequent generations?
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KEY CONCEPT Populations, not
individuals, evolve.The phenotypes for a certain trait in a population can be
graphed in what is called a phenotypic distribution. In this type of graph, you can see the range of
phenotypes present in the population. You can also see how common each of these phenotypes is in the
population, as measured by its frequency. For a trait that is not undergoing natural selection,
the intermediate phenotype is the most common phenotype in the population, while the extreme
phenotypes are less common. A frequency distribution for this type of trait looks like a bell-shaped
curve. A type of distribution in which the frequency is highest near the mean and decreases toward
each extreme is called a normal distribution.Natural selection can cause a phenotypic
distribution to change in one of three ways: • Directional selection favors
phenotypes at one extreme of a trait’s range. This type of selection causes the entire
bell-shaped curve to shift in one direction or the other, toward the phenotype that is advantageous.
During directional selection, the mean (or average) phenotype
changes.
• Stabilizing selection favors intermediate
phenotypes, selecting against phenotypes at both extremes of a trait’s range. This type of
selection causes the peak of the bell-shaped curve to become taller and more narrow (more
“stable”), since the intermediate phenotype is becoming more and more common in the
population.
• Disruptive selection favors phenotypes at
both extreme’s of a trait’s range, selecting against intermediate phenotypes. This type
of selection disrupts the distribution by causing a “dip” in the center of the
bell-shaped curve, since the intermediate phenotype is becoming less and less common in the
population.
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18.
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What is shown in a phenotypic
distribution?
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19.
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In what type of situation does a phenotypic
distribution look like a bell-shaped curve?
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20.
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What is a normal distribution?
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21.
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Name and describe the three (3) ways in which
natural selection can change the distribution of a trait.
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Section Quiz 11.2: Natural
Selection in Populations
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22.
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What is the observable change in the allele frequencies of a population over
time called?
A. | selection | B. | microevolution | C. | distribution | D. | recombination |
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23.
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Natural selection that changes the distribution of a trait to favor one extreme
phenotype is called
A. | disruptive selection. | B. | stabilizing selection. | C. | normalizing
selection. | D. | directional selection. |
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24.
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In stabilizing selection, what occurs in a population?
A. | The population shifts toward one of two extreme phenotypes. | B. | Both extreme
phenotypes shift toward the middle. | C. | The intermediate phenotype becomes more
common. | D. | The intermediate phenotype becomes rare. |
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25.
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A population that is not undergoing natural selection displays what type
of distribution?
A. | normal | B. | disruptive | C. | directional | D. | stabilizing |
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26.
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In a population of birds, intermediate beak size is selected against, and both
very small and very large beak sizes are favored. What type of selection is this an example
of?
A. | directional | B. | disruptive | C. | normal | D. | stabilizing |
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