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Evolutionary Outcomes
MCQ questions and answers.
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MCQ Questions
1. What is the main evolutionary outcome of directional selection in a population?
A.
The population mean shifts toward one extreme phenotype
B.
The population mean remains exactly unchanged
C.
Both extreme phenotypes become more common
D.
All phenotypes disappear except the intermediate phenotype
Correct Answer:
The population mean shifts toward one extreme phenotype
Explanation:
Directional selection favors one extreme phenotype, so the average trait value of the population shifts toward that extreme over generations.
2. What is the typical outcome of stabilising selection on a population?
A.
Intermediate phenotypes become more common
B.
One extreme phenotype becomes the only phenotype
C.
Both extreme phenotypes increase in frequency
D.
The population splits into two distinct groups
Correct Answer:
Intermediate phenotypes become more common
Explanation:
Stabilising selection favors intermediate phenotypes and reduces the frequency of extreme phenotypes, making the population more uniform around the average.
3. Which evolutionary outcome is most closely associated with disruptive selection?
A.
An increase in both extreme phenotypes
B.
An increase only in the intermediate phenotype
C.
A shift toward one extreme phenotype only
D.
A complete loss of variation in the population
Correct Answer:
An increase in both extreme phenotypes
Explanation:
Disruptive selection favors both extreme phenotypes over the intermediate phenotype, increasing variation within the population.
4. How does directional selection affect the average value of a trait?
A.
It moves the average toward one extreme
B.
It always moves the average toward the middle
C.
It makes the average value equal to both extremes
D.
It removes any change in the average value
Correct Answer:
It moves the average toward one extreme
Explanation:
Because one extreme phenotype is favored, the average value of the trait shifts in the direction of that favored extreme.
5. What happens to phenotypic variation under stabilising selection?
A.
It generally decreases
B.
It always doubles
C.
It changes only toward one extreme
D.
It becomes equal in all individuals
Correct Answer:
It generally decreases
Explanation:
Stabilising selection removes or reduces extreme phenotypes, so the range of phenotypic variation generally becomes smaller.
6. Which selection type can produce two distinct groups of phenotypes in a population?
A.
Disruptive selection
B.
Stabilising selection
C.
Directional selection
D.
No natural selection
Correct Answer:
Disruptive selection
Explanation:
Disruptive selection favors both extremes and may cause the population to become divided into two distinct phenotype groups.
7. What is a possible long-term evolutionary outcome of disruptive selection?
A.
The population may become divided into separate groups
B.
The population always becomes uniform
C.
Only intermediate individuals survive
D.
The population loses all extreme traits
Correct Answer:
The population may become divided into separate groups
Explanation:
By favoring two extreme phenotypes, disruptive selection can separate a population into groups with different characteristics.
8. Which selection type usually maintains the average phenotype in a population?
A.
Stabilising selection
B.
Directional selection
C.
Disruptive selection
D.
Selection favoring one extreme
Correct Answer:
Stabilising selection
Explanation:
Stabilising selection favors the average or intermediate phenotype, so the population mean usually remains close to the original average.
9. A population becomes more common in a form that is larger than its original average. Which outcome is shown?
A.
A shift toward one extreme phenotype
B.
A reduction of both extreme phenotypes
C.
An increase in only intermediate phenotypes
D.
A split into two equally common extreme groups
Correct Answer:
A shift toward one extreme phenotype
Explanation:
An increase in a larger-than-average form indicates that the population is shifting toward one extreme, which is the outcome of directional selection.
10. Which statement correctly compares stabilising and disruptive selection?
A.
Stabilising selection favors intermediates, while disruptive selection favors extremes
B.
Both favor only one extreme phenotype
C.
Stabilising selection favors extremes, while disruptive selection favors intermediates
Explanation:
Stabilising selection increases the frequency of intermediate phenotypes, whereas disruptive selection increases the frequency of both extreme phenotypes.
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Evolutionary Outcomes
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