1. What happens to intermediate phenotypes during selection against intermediate phenotypes?
A.
They are selected against
B.
They are always selected for
C.
They become the only surviving forms
D.
They are changed into identical phenotypes
Correct Answer:
They are selected against
Explanation:
Selection against intermediate phenotypes reduces the survival or reproduction of individuals with intermediate traits.
2. Selection against intermediate phenotypes is characteristic of which type of natural selection?
A.
Directional selection
B.
Stabilising selection
C.
Disruptive selection
D.
Artificial selection
Correct Answer:
Disruptive selection
Explanation:
Disruptive selection favours individuals at both extremes and selects against individuals with intermediate phenotypes.
3. In disruptive selection, which individuals are generally favoured?
A.
Only individuals with intermediate traits
B.
Individuals with traits at both extremes
C.
Only individuals with the average trait
D.
Individuals with no observable trait
Correct Answer:
Individuals with traits at both extremes
Explanation:
Disruptive selection favours both extreme phenotypes while reducing the success of intermediate phenotypes.
4. What may happen to a population when intermediate phenotypes are selected against for many generations?
A.
It may develop two distinct forms
B.
It always develops only one form
C.
All individuals become intermediate
D.
Variation disappears completely
Correct Answer:
It may develop two distinct forms
Explanation:
When intermediate individuals are selected against, the two extreme forms may become more common and create two distinct groups.
5. Which pattern of survival shows selection against intermediate phenotypes?
A.
High survival of intermediate individuals only
B.
Equal survival of all individuals
C.
High survival of both extreme forms and low survival of intermediate forms
D.
Low survival of both extreme forms and high survival of intermediate forms
Correct Answer:
High survival of both extreme forms and low survival of intermediate forms
Explanation:
This survival pattern directly represents disruptive selection, in which intermediate phenotypes have lower fitness than both extremes.
6. A population contains small and large individuals, while medium-sized individuals survive poorly. Which selection is occurring?
A.
Disruptive selection
B.
Stabilising selection
C.
Directional selection
D.
Random mating
Correct Answer:
Disruptive selection
Explanation:
The small and large individuals are favoured, whereas the intermediate-sized individuals are selected against.
7. What is the effect of selection against intermediate phenotypes on the frequency of extreme phenotypes?
A.
Their frequency may increase
B.
Their frequency always becomes zero
C.
Their frequency must remain unchanged
D.
Their frequency decreases because intermediates are favoured
Correct Answer:
Their frequency may increase
Explanation:
When intermediate phenotypes have lower survival or reproduction, the favoured extreme phenotypes may become more common.
8. Which statement correctly describes selection against intermediate phenotypes?
A.
The average phenotype has the highest fitness
B.
Both extreme phenotypes have higher fitness than the intermediate phenotype
C.
Only one extreme phenotype has higher fitness
D.
All phenotypes have the same fitness
Correct Answer:
Both extreme phenotypes have higher fitness than the intermediate phenotype
Explanation:
In selection against intermediate phenotypes, both extreme forms are favoured over the intermediate form.
9. If birds with very small or very large beaks obtain food more successfully than birds with medium-sized beaks, what type of selection is shown?
A.
Stabilising selection
B.
Directional selection
C.
Disruptive selection
D.
No natural selection
Correct Answer:
Disruptive selection
Explanation:
The two extreme beak sizes are favoured and the intermediate beak size is selected against, which is disruptive selection.
10. Selection against intermediate phenotypes can increase which type of variation in a population?
A.
Differences between the two extreme forms
B.
Only the number of intermediate forms
C.
Uniformity of all individuals
D.
The absence of phenotypic differences
Correct Answer:
Differences between the two extreme forms
Explanation:
By reducing intermediate individuals and favouring both extremes, this selection can increase differences between the two extreme forms.
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