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Beak Size Variation
MCQ questions and answers.
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MCQ Questions
1. In a bird population, birds with larger beaks are better able to eat hard seeds and produce more offspring. Which type of selection is shown?
A.
Directional selection
B.
Stabilising selection
C.
Disruptive selection
D.
Artificial selection
Correct Answer:
Directional selection
Explanation:
Directional selection favors one extreme beak size, causing the population's average beak size to shift toward larger beaks.
2. If birds with medium-sized beaks survive better than birds with very small or very large beaks, which type of selection occurs?
A.
Directional selection
B.
Stabilising selection
C.
Disruptive selection
D.
Sexual selection
Correct Answer:
Stabilising selection
Explanation:
Stabilising selection favors the intermediate beak size and selects against both extreme beak sizes.
3. In a bird population, both very small and very large beaks are favored, while medium-sized beaks are less successful. What type of selection is this?
A.
Stabilising selection
B.
Directional selection
C.
Disruptive selection
D.
Artificial selection
Correct Answer:
Disruptive selection
Explanation:
Disruptive selection favors both extreme beak sizes and selects against the intermediate beak size.
4. A population of birds has an average beak size that becomes larger over generations because large-beaked birds obtain more food. What has occurred?
A.
A shift toward larger beaks
B.
A shift toward medium beaks
C.
A loss of all beak variation
D.
A shift toward smaller beaks
Correct Answer:
A shift toward larger beaks
Explanation:
When large-beaked birds survive and reproduce more successfully, the average beak size shifts toward the larger extreme.
5. Which beak size is favored by stabilising selection in a bird population?
A.
Only the smallest beak
B.
Only the largest beak
C.
The intermediate-sized beak
D.
Both extreme beak sizes
Correct Answer:
The intermediate-sized beak
Explanation:
Stabilising selection favors the average or intermediate beak size and reduces the success of extreme sizes.
6. Disruptive selection acting on beak size can produce a population with which pattern?
A.
Mostly medium-sized beaks
B.
Mostly small and large beaks
C.
Only large beaks
D.
No variation in beak size
Correct Answer:
Mostly small and large beaks
Explanation:
Disruptive selection favors both small and large beaks, so these two extreme forms become more common than medium-sized beaks.
7. A change in available food favors birds with smaller beaks over birds with larger beaks. Which selection pattern is most likely?
Explanation:
Directional selection occurs when one extreme, in this case the smaller beak, has an advantage over other sizes.
8. Which statement best describes beak size variation under directional selection?
A.
One extreme beak size is favored
B.
Both extreme beak sizes are favored equally
C.
The intermediate beak size is favored
D.
All beak sizes have the same advantage
Correct Answer:
One extreme beak size is favored
Explanation:
Directional selection favors one extreme beak size and shifts the population average in that direction.
9. If medium-sized beaks are most efficient for feeding and are favored, what happens to the extreme beak sizes?
A.
They become more successful than medium beaks
B.
They are selected against
C.
They become the only beak sizes present immediately
D.
They are always favored equally
Correct Answer:
They are selected against
Explanation:
In stabilising selection, medium-sized beaks have the highest survival or feeding success, while very small and very large beaks are selected against.
10. A bird population feeds on two types of seeds: very small and very large. Birds with small or large beaks feed well, but birds with medium beaks feed poorly. Which selection type is expected?
A.
Directional selection
B.
Stabilising selection
C.
Disruptive selection
D.
No selection
Correct Answer:
Disruptive selection
Explanation:
The two different food sizes favor two extreme beak sizes, while medium beaks are less successful, showing disruptive selection.
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