The question
Name: ______________________ Date: ____________ Drift in small and large populations (4 points)
Experimental setup
Two wildflower populations
A wildflower has purple or white flowers, controlled by one gene; the allele for white flowers is recessive. Flower color makes no difference to which plants are visited by pollinators, survive or set seed. Population 1 has about 5,000 flowering plants in a large meadow. Population 2 has about 25 flowering plants on a rocky hilltop 30 km away, and no pollen or seeds pass between the two. In 1990 the frequency of the white allele was 0.30 in both populations.
(a) Describe genetic drift. [1 point]
(b) Explain why the frequency of the white allele is expected to change more in population 2 than in population 1 over the next 20 generations. [1 point]
(c) Predict how the genetic variation for flower color in population 2 will change over many generations if the population stays small and isolated. Justify your prediction. [1 point]
(d) Bees begin to carry pollen between the two populations every year. Predict the effect on the difference between the white-allele frequencies of the two populations, and justify your prediction. [1 point]