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Question #45558
The Question
Darwinian fitness is fundamentally measured by reproductive success. However, in a small, isolated population of an endangered mammal, researchers observe a steadily increasing frequency of a recessive allele that causes complete infertility in homozygous individuals. Which of the following best explains this evolutionary anomaly and its ecological consequence?
Options
- A.
Balancing selection is maintaining the allele in heterozygotes, thereby increasing the population's intrinsic rate of natural increase (r).
- B.
Genetic drift is overriding purifying selection, creating a genetic load that severely restricts the population from realizing its biotic potential.
- C.
The population is experiencing a founder effect that enhances its Darwinian fitness by actively purging deleterious mutations.
- D.
Directional selection is favoring the recessive allele due to environmental stress, thereby expanding the carrying capacity (K) of the habitat.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Infertility Definition|Allele Frequency Drift|Ecological Fitness (Darwinian Fitness)
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often assume Natural Selection is always the dominant evolutionary force.
The trap lies in failing to recognize that in small populations, Genetic Drift can completely override purifying selection, leading to the increase of deleterious (even sterile) alleles.
This question synthesizes Population Genetics (Drift vs.
Selection) with Ecology (Biotic Potential vs.
Genetic Load).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Reproductive Health - Class 12 |
| Concept | Infertility Definition |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |