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Directional Selection Definition
MCQ questions and answers.
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MCQ Questions
1. What is directional selection?
A.
Natural selection that favors individuals at one extreme of a trait
B.
Natural selection that favors individuals with average traits
C.
Natural selection that favors both extreme forms of a trait
D.
Random change in the frequency of traits
Correct Answer:
Natural selection that favors individuals at one extreme of a trait
Explanation:
Directional selection occurs when one extreme phenotype is favored, causing the population's trait distribution to shift toward that extreme.
2. In directional selection, which type of phenotype is generally favored?
A.
The average phenotype only
B.
One extreme phenotype
C.
Both extreme phenotypes equally
D.
Every phenotype equally
Correct Answer:
One extreme phenotype
Explanation:
Directional selection favors one extreme form of a characteristic rather than the average or both extremes.
3. What is the usual effect of directional selection on a population's average trait value?
A.
It shifts toward one extreme
B.
It always remains unchanged
C.
It shifts toward the middle
D.
It disappears completely
Correct Answer:
It shifts toward one extreme
Explanation:
Because one extreme phenotype is favored, the average value of the trait tends to move in that direction over generations.
4. Which statement best describes directional selection?
A.
It favors a single extreme variation of a trait
B.
It favors only intermediate variations of a trait
C.
It favors two opposite extreme variations equally
D.
It produces no change in inherited traits
Correct Answer:
It favors a single extreme variation of a trait
Explanation:
The defining feature of directional selection is selection for one extreme variation of an inherited trait.
5. If larger individuals are consistently favored in a population, what type of selection is occurring?
A.
Directional selection
B.
Stabilising selection
C.
Disruptive selection
D.
No natural selection
Correct Answer:
Directional selection
Explanation:
Favoring one extreme, such as larger body size, is characteristic of directional selection.
6. Which change would indicate directional selection for body size?
A.
The population gradually becomes larger on average
B.
The population remains centered around the original average size
C.
Both very small and very large individuals become more common
D.
All body sizes become equally common
Correct Answer:
The population gradually becomes larger on average
Explanation:
A gradual shift in the population average toward larger body size shows that one extreme is being favored.
7. Directional selection causes a population to move toward which part of the range of a trait?
A.
One end of the range
B.
The exact center of the range
C.
Both ends of the range equally
D.
A random part of the range without selection
Correct Answer:
One end of the range
Explanation:
Directional selection favors one end, or extreme, of the variation present in a population.
8. Which example represents directional selection?
A.
Individuals with longer beaks have greater reproductive success
B.
Individuals with medium-sized bodies have greater reproductive success
C.
Individuals with either very short or very long beaks have greater reproductive success
D.
All individuals have the same reproductive success
Correct Answer:
Individuals with longer beaks have greater reproductive success
Explanation:
Longer beaks represent one extreme, so increased success of these individuals is an example of directional selection.
9. What happens to the favored extreme phenotype during directional selection?
A.
It becomes more common over generations
B.
It becomes less common over generations
C.
It is always removed immediately
D.
It changes into the average phenotype in one generation
Correct Answer:
It becomes more common over generations
Explanation:
Individuals with the favored extreme phenotype are more likely to survive or reproduce, so that phenotype tends to increase in frequency.
10. Which phrase is most closely associated with the definition of directional selection?
A.
Selection favoring one extreme
B.
Selection favoring the average
C.
Selection favoring both extremes
D.
Selection without any difference in reproductive success
Correct Answer:
Selection favoring one extreme
Explanation:
Directional selection is defined by the advantage given to one extreme phenotype of a trait.
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