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Question #46455
The Question
An alien predator species is introduced into an isolated lake, causing a drastic 95% reduction in the native fish population. In the small surviving population, a previously rare allele for a specific fin shape—which offers no survival or reproductive advantage—rapidly reaches a frequency of 1.0 over a few generations. Which of the following statements regarding this evolutionary event is INCORRECT?
Options
- A.
The drastic reduction in population size induced a genetic bottleneck, causing non-directional changes in allele frequencies.
- B.
The rapid fixation of the rare allele demonstrates directional natural selection driven by the new ecological pressure.
- C.
The change in allele frequency occurred due to stochastic sampling error, independent of the allele's adaptive value.
- D.
The surviving sub-population will exhibit reduced genetic variability and an increased probability of homozygosity.
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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
Allele Frequency Drift|Alien Species Invasion Impacts|Founder Effect
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often conflate 'rapid evolutionary change following an environmental stressor' with 'Natural Selection'.
The trap relies on the assumption that if an allele becomes fixed after a survival event (alien invasion), it must have provided a hidden adaptive advantage.
However, in drastically reduced populations (bottlenecks), stochastic sampling error (Genetic Drift) overpowers selection, frequently fixing neutral or even maladaptive alleles.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Evolution - Class 12 |
| Concept | Allele Frequency Drift |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |