Populations of the grass Agrostis capillaris growing on copper-mine tailings (contaminated soil) and on adjacent uncontaminated pastures are within wind-pollination range of one another. Despite continuous gene flow between these two populations, they exhibit distinct, stable differences in copper tolerance. Which of the following statements best explains how natural selection maintains this genetic divergence?
Wind pollination acts as a directional transport mechanism that selectively deposits pollen containing the tolerance allele onto contaminated soils.
Intense selection pressure against tolerant plants on uncontaminated pasture, and against non-tolerant plants on contaminated mine tailings, outweighs the homogenizing effect of gene flow.
Stabilizing selection operates equally across both habitats, ensuring that both populations maintain high phenotypic plasticity rather than genetic divergence.
Genetic drift randomly increases the frequency of the non-tolerant allele in the pasture population at a rate that exactly balances the incoming gene flow.
38 exam-style questions on OCR GCSE Biology 5.2 Natural selection and evolution, covering 5.2.1 Genetic variation within a population, 5.2.2 Developments in classification systems, 5.2.3 How evolution occurs through natural selection, 5.2.4 Evolution as change over time, 5.2.5 Evidence for evolution, and 5.2.6 Darwin and Wallace. Each one has a worked solution and a mark scheme showing where the marks go.