Before You Begin
Question #45838
The Question
A small population of a mammalian species with narrow thermal tolerance survives a severe climatic bottleneck and becomes geographically isolated. Over subsequent generations, an unusually high frequency of a rare autosomal recessive disorder is observed in this population compared to the original mainland group. Which of the following is the most accurate evolutionary explanation for this observation?
Options
- A.
The climatic stress acted as an environmental mutagen, significantly increasing the mutation rate and generating new recessive alleles.
- B.
Genetic drift via the founder effect occurred, leading to a drastically reduced gene pool and increased homozygosity due to inbreeding.
- C.
Directional selection favored the recessive phenotype, as the bottleneck event selectively eliminated all dominant alleles.
- D.
The geographical isolation prevented gene flow, causing the population to strictly maintain Hardy-Weinberg equilibrium.
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
Pedigree Analysis Traps|Thermal Tolerance Ranges|Population Growth Model Dynamics
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between Genetic Drift (statistical changes in allele frequency due to small population size) and Environmental Mutagenesis.
Students often misattribute the sudden high frequency of a recessive trait in an isolated, stressed population to the environment 'causing' new mutations, rather than recognizing the effects of a reduced allelic pool and increased homozygosity (consanguinity) following a bottleneck.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Principles of Inheritance and Variation - Class 12 |
| Concept | Pedigree Analysis Traps |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |