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Stabilising Selection Graph
MCQ questions and answers.
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MCQ Questions
1. What happens to the graph of a population after stabilising selection?
A.
It becomes narrower around the average value
B.
It shifts completely toward one extreme
C.
It develops two separate peaks
D.
It becomes a straight horizontal line
Correct Answer:
It becomes narrower around the average value
Explanation:
In a stabilising selection graph, individuals with average traits are favoured, so the distribution becomes narrower around the mean.
2. In a stabilising selection graph, which individuals are selected against?
A.
Individuals with average traits
B.
Individuals at both extremes
C.
Only individuals at one extreme
D.
All individuals equally
Correct Answer:
Individuals at both extremes
Explanation:
The graph shows reduced numbers of individuals with extreme phenotypes because stabilising selection favours intermediate traits.
3. What usually happens to the mean phenotype in a stabilising selection graph?
A.
It remains approximately unchanged
B.
It moves toward the lower extreme
C.
It moves toward the higher extreme
D.
It disappears from the graph
Correct Answer:
It remains approximately unchanged
Explanation:
Stabilising selection reduces variation at both extremes while keeping the average phenotype nearly the same.
4. Which shape best represents the population distribution after stabilising selection?
A.
A taller and narrower bell-shaped curve
B.
A curve shifted entirely to the left
C.
A curve with two equal peaks
D.
A flat line across the graph
Correct Answer:
A taller and narrower bell-shaped curve
Explanation:
The post-selection graph is usually taller and narrower because more individuals have the intermediate phenotype.
5. What does the horizontal axis usually represent in a stabilising selection graph?
A.
Phenotypic variation or trait values
B.
Number of generations only
C.
Rate of mutation
D.
Number of species in an ecosystem
Correct Answer:
Phenotypic variation or trait values
Explanation:
The horizontal axis displays the different values of the trait, from one extreme through the average to the other extreme.
6. What does the vertical axis usually represent in a stabilising selection graph?
A.
Frequency of individuals
B.
Body temperature only
C.
Number of genes in one chromosome
D.
Age of the population
Correct Answer:
Frequency of individuals
Explanation:
The vertical axis shows how many individuals have each phenotype or trait value.
7. In a graph of stabilising selection, where is the highest point generally found after selection?
A.
Near the intermediate phenotype
B.
At the lowest extreme phenotype
C.
At the highest extreme phenotype
D.
Outside the range of phenotypes
Correct Answer:
Near the intermediate phenotype
Explanation:
Intermediate phenotypes are favoured, so the peak of the graph is near the average trait value.
8. Which change in a bell-shaped graph indicates reduced variation due to stabilising selection?
A.
The curve becomes narrower
B.
The curve moves only to the right
C.
The curve forms two peaks
D.
The curve loses its central peak
Correct Answer:
The curve becomes narrower
Explanation:
A narrower curve indicates that fewer individuals have extreme traits and that variation around the mean has decreased.
9. A stabilising selection graph shows fewer individuals at both ends and more individuals in the centre. What does this indicate?
A.
Intermediate traits are favoured
B.
Both extreme traits are favoured
C.
Only the left extreme is favoured
D.
No phenotype is favoured
Correct Answer:
Intermediate traits are favoured
Explanation:
The central increase and reduction at both ends are the characteristic graphical pattern of stabilising selection.
10. Which statement correctly describes the two curves commonly shown in a stabilising selection graph?
A.
The post-selection curve is narrower than the original curve
B.
The post-selection curve shifts to one extreme
C.
The post-selection curve has two peaks
D.
The original curve has no variation
Correct Answer:
The post-selection curve is narrower than the original curve
Explanation:
The original curve shows the population before selection, while the narrower post-selection curve shows reduced variation around the same mean.
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