biology : class12 Environmental Change and Selection : Directional Selection, Stabilising Selection, Disruptive Selection : Types of Natural Selection MCQ Questions and Answers
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Environmental Change and Selection
MCQ questions and answers.
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MCQ Questions
1. When an environment changes, which type of natural selection may increase the frequency of traits that are better suited to the new conditions?
A.
Directional selection
B.
Random selection
C.
Artificial selection
D.
No selection
Correct Answer:
Directional selection
Explanation:
Directional selection favors individuals with one extreme form of a trait when environmental conditions change, causing that trait to become more common.
2. A colder environment favors mice with thicker fur. Which pattern of selection is most likely to occur?
Explanation:
The colder environment gives mice with thicker fur an advantage, so selection shifts the population toward that extreme.
3. After an environmental change, which individuals are most likely to survive and reproduce?
A.
Individuals best adapted to the new conditions
B.
Individuals with the rarest traits only
C.
Individuals that are largest in every environment
D.
Individuals chosen by other organisms
Correct Answer:
Individuals best adapted to the new conditions
Explanation:
Environmental change alters survival pressures, so organisms with traits suited to the new conditions are more likely to reproduce.
4. If an environment remains stable and favors average-sized individuals, which type of selection is likely?
A.
Stabilising selection
B.
Directional selection
C.
Disruptive selection
D.
Artificial selection
Correct Answer:
Stabilising selection
Explanation:
Stabilising selection favors intermediate traits when the environment consistently suits average forms better than either extreme.
5. A change in climate makes smaller beaks more useful for feeding on newly common small seeds. What may happen to the bird population?
A.
Small-beaked birds may become more common
B.
All birds will immediately develop small beaks
C.
Beak variation will always disappear
D.
Large-beaked birds will always be favored
Correct Answer:
Small-beaked birds may become more common
Explanation:
If the changed environment favors smaller beaks, birds with that inherited trait may survive and reproduce more successfully.
6. An environmental change creates two different food sources, favoring birds with either very short or very long beaks. Which selection pattern may result?
A.
Disruptive selection
B.
Stabilising selection
C.
Directional selection toward average beaks
D.
No selection
Correct Answer:
Disruptive selection
Explanation:
Disruptive selection favors both extremes when environmental conditions provide advantages to two different forms of a trait.
7. Why can environmental change lead to a change in the frequency of traits in a population?
A.
Different traits may affect survival and reproduction differently
B.
All organisms change their genes because they need to
C.
The environment directly changes every inherited trait
D.
Selection stops when the environment changes
Correct Answer:
Different traits may affect survival and reproduction differently
Explanation:
Environmental conditions determine which inherited traits provide advantages, changing the reproductive success of individuals.
8. If pollution makes dark tree bark common, dark moths may become more common because they are harder for predators to see. This is an example of selection caused by what?
A.
Environmental change
B.
Unrelated mating behavior
C.
The disappearance of variation
D.
Equal survival of all moths
Correct Answer:
Environmental change
Explanation:
Pollution changes the background color of the habitat, giving better camouflage and a survival advantage to dark moths.
9. When a new predator enters an ecosystem, which outcome is possible?
A.
Traits that help organisms avoid the predator may become more common
B.
All organisms will become identical
C.
Natural selection will stop permanently
D.
Every organism will gain the same protective trait
Correct Answer:
Traits that help organisms avoid the predator may become more common
Explanation:
A new predator changes selection pressures, so inherited traits that improve escape or protection may be favored.
10. If environmental conditions change from favoring average-sized organisms to favoring larger organisms, what type of selection may occur?