Examkin

Question

Difficulty: Very hardModern Evolutionary Theory and Genetic Basis of Evolution

In a stable mainland population of a wildflower species, the frequency of a recessive allele (aa) causing albino foliage is 0.30.3. A small group of 10 seed-bearing plants is accidentally carried by wind to an isolated oceanic island where no other members of the species exist. In the newly established island colony, the frequency of allele aa is found to be 0.70.7 purely due to sampling chance during colonization. Which evolutionary force best accounts for this rapid change in allele frequency, and what is its primary consequence on the island's gene pool?

  1. Genetic drift via the founder effect, which reduces overall genetic variation in the new population regardless of natural selection.Answer
  2. B
    Directional natural selection, which favors the albino phenotype to enhance photosynthetic efficiency under island sunlight.
  3. C
    Environmentally induced mutation, which causes green plants to alter their germline DNA to cope with new atmospheric conditions.
  4. D
    Gene flow, which continuously transfers traits from the mainland to create continuous phenotypic variation across island habitats.

Answer

Genetic drift via the founder effect, which reduces overall genetic variation in the new population regardless of natural selection.
The correct answer identifies the founder effect—a key mechanism of genetic drift in modern evolutionary theory. When a small group of individuals colonizes a new geographical area, the alleles carried by the founders determine the new gene pool. By chance alone, allele frequencies in the colonizing group differ markedly from the source population, which decreases overall genetic diversity independently of natural selection.

Step-by-Step Solution

1
Analyze the cause of the allele frequency shift in the population
A very small sample size (10 plants) colonized an isolated island, shifting the recessive allele frequency from 0.30.3 to 0.70.7 purely due to sampling chance.
When a small fragment of a population colonizes a new area, the allele frequencies of the founders rarely match the ancestral gene pool.
2
Identify the primary evolutionary mechanism
Random fluctuations in allele frequency resulting from small colony founding represent the founder effect, a form of genetic drift.
Genetic drift acts randomly on allele frequencies without regard to reproductive fitness or adaptive advantage.
3
Evaluate option claims against modern evolutionary genetics
The founder effect reduces overall genetic diversity because only a portion of the original population's alleles are represented in the new colony.
Natural selection, direct environmental mutation induction, and gene flow fail to explain an allele frequency shift caused by random sampling during reproductive isolation.

Key Concept

Genetic drift and the Founder effect in Modern Evolutionary Theory
Rate this question

Topics

Modern Evolutionary Theory and Genetic Basis of Evolution

More questions from this topic