biology : class12 Increase in Phenotypic Variation : Directional Selection, Stabilising Selection, Disruptive Selection : Types of Natural Selection MCQ Questions and Answers
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Increase in Phenotypic Variation
MCQ questions and answers.
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MCQ Questions
1. Which type of natural selection can increase phenotypic variation in a population?
A.
Directional selection
B.
Stabilising selection
C.
Disruptive selection
D.
Artificial selection
Correct Answer:
Disruptive selection
Explanation:
Disruptive selection favours individuals at both extremes of a phenotype and selects against intermediate forms, increasing phenotypic variation.
2. What is the usual effect of disruptive selection on phenotypic variation?
A.
It decreases variation by favouring the average phenotype
B.
It increases variation by favouring extreme phenotypes
C.
It completely removes all phenotypes
D.
It changes only the age of individuals
Correct Answer:
It increases variation by favouring extreme phenotypes
Explanation:
By favouring two different extreme phenotypes, disruptive selection maintains or increases differences among individuals in the population.
3. In disruptive selection, which individuals are generally favoured?
A.
Only individuals with intermediate traits
B.
Individuals with both extreme forms of a trait
C.
Only the smallest individuals
D.
Individuals with no observable traits
Correct Answer:
Individuals with both extreme forms of a trait
Explanation:
Disruptive selection favours individuals at both ends of a phenotypic range, which contributes to increased phenotypic variation.
4. A bird population contains birds with small, medium, and large beaks. If birds with small and large beaks survive better than birds with medium beaks, what happens to phenotypic variation?
A.
It increases
B.
It disappears immediately
C.
It becomes limited to medium beaks
D.
It remains unchanged in every generation
Correct Answer:
It increases
Explanation:
Survival of birds with both small and large beaks, while medium-beaked birds are selected against, promotes greater phenotypic variation.
5. Which pattern of selection is most likely to produce two distinct phenotypic groups in a population?
A.
Disruptive selection
B.
Stabilising selection
C.
Directional selection
D.
No selection
Correct Answer:
Disruptive selection
Explanation:
Disruptive selection favours two extreme phenotypes and can separate a population into two distinct phenotypic groups.
6. Why can disruptive selection increase phenotypic variation?
A.
It favours only the average phenotype
B.
It favours different extreme phenotypes in the same population
C.
It prevents all individuals from reproducing
D.
It removes differences between individuals
Correct Answer:
It favours different extreme phenotypes in the same population
Explanation:
When different extreme forms are favoured, more than one type of phenotype is maintained, increasing variation within the population.
7. Which selection pattern is represented when both very light and very dark individuals are favoured over medium-coloured individuals?
A.
Directional selection
B.
Stabilising selection
C.
Disruptive selection
D.
Random selection
Correct Answer:
Disruptive selection
Explanation:
Favouring both colour extremes while selecting against the intermediate colour is characteristic of disruptive selection, which increases phenotypic variation.
8. Compared with stabilising selection, disruptive selection usually causes phenotypic variation to:
A.
Increase
B.
Decrease
C.
Become completely absent
D.
Remain exactly the same
Correct Answer:
Increase
Explanation:
Stabilising selection favours intermediate phenotypes, whereas disruptive selection favours extremes and therefore tends to increase phenotypic variation.
9. A population of insects has green and brown individuals. If both colours are better camouflaged in different habitats and survive better than intermediate-coloured insects, which result is expected?
A.
Greater phenotypic variation
B.
Only the intermediate colour will remain
C.
All insects will become identical
D.
Phenotypic variation will always decrease
Correct Answer:
Greater phenotypic variation
Explanation:
When two contrasting phenotypes are favoured in different conditions, disruptive selection maintains both forms and increases phenotypic variation.
10. Which statement correctly describes the relationship between disruptive selection and phenotypic variation?
A.
Disruptive selection favours intermediate traits and reduces variation
B.
Disruptive selection favours extreme traits and can increase variation
C.
Disruptive selection affects only inherited diseases
D.
Disruptive selection removes both extreme traits
Correct Answer:
Disruptive selection favours extreme traits and can increase variation
Explanation:
The survival and reproduction of individuals with extreme phenotypes, combined with selection against intermediates, can increase phenotypic variation.
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