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Question #46460
The Question
While studying a critically endangered population of Panthera tigris reduced to just 15 individuals, conservation geneticists note the sudden fixation of a slightly deleterious allele that causes a minor skeletal defect. Historically, directional selection kept this allele at a frequency of <0.01. Which of the following statements accurately describes the evolutionary mechanics responsible for this observation?
Options
- A.
Genetic drift acted as a deterministic force, actively favoring the deleterious allele to increase the population's overall genetic diversity.
- B.
The stochastic fluctuations of genetic drift overpowered the deterministic purging effect of directional selection due to the small effective population size.
- C.
Directional selection shifted the adaptive optimum, converting the previously deleterious allele into a beneficial one to prevent species extinction.
- D.
The Hardy-Weinberg equilibrium was re-established in the small population, allowing the recessive deleterious allele to naturally reach fixation.
Check Your Answer
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
Hardy-Weinberg Equilibrium|Genetic Bottleneck|Founder Effect
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often view Natural Selection as an absolute, omnipotent force that always optimizes fitness.
The trap lies in failing to recognize that Genetic Drift is a stochastic (random) process whose strength is inversely proportional to population size.
In small populations, drift can overpower the deterministic nature of directional selection, leading to the counterintuitive fixation of deleterious alleles.
Distractors exploit teleological thinking (Option C) and fundamental misunderstandings of Hardy-Weinberg conditions (Option D).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Evolution - Class 12 |
| Concept | Natural Selection Directionality |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |