In a large, isolated population of a plant species, a catastrophic flood randomly eliminates over of the individuals regardless of their phenotypic traits. The few surviving individuals repopulate the area, resulting in allele frequencies in the restored population that differ significantly from those of the original gene pool. According to modern evolutionary theory (Neo-Darwinism), which mechanism is primarily responsible for this shift in allele frequencies?
- Genetic drift via the bottleneck effect, where random sampling changes allele frequencies in small surviving populations.Answer
- BDirectional natural selection, where environmental stress favors specific advantageous survival phenotypes.
- CEnvironmentally induced mutation, where flood stress directly induced new beneficial alleles in the survivors.
- DGene flow, where foreign alleles were introduced into the gene pool by immigrating individuals.
Answer
Genetic drift via the bottleneck effect, where random sampling changes allele frequencies in small surviving populations.
The correct answer correctly identifies genetic drift through the bottleneck effect. When a population undergoes an unselective, catastrophic reduction in size, the small surviving subgroup represents an arbitrary random sample of the original gene pool. As this subgroup reproduces, the resulting allele frequencies differ randomly from the original population, which is a classic demonstration of genetic drift in modern evolutionary biology.
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Key Concept
Genetic Drift and Bottleneck Effect in Modern Evolutionary Synthesis