Exam 6: The Ways of Change: Drift and Selection

Contrast evolution by natural selection with evolution by genetic drift.

Why was Charles II of Spain, of the Hapsburg dynasty, called el hechizado, the "hexed"?

How do gene frequencies behave in Hardy-Weinberg equilibrium?

In the Hardy-Weinberg equation, q is

Why might an endangered species, whose population numbers are already low, be even more threatened to extinction because of inbreeding?

Earth's biotic and abiotic environments are changing rapidly due, in part, to human activities. For example, the introduction of non-native invasive species into new habitats and climate change highlight two ways in which humans are altering the environment experienced by other species. Some species will probably adapt to these changes, while others may not. Considering the processes of mutation, natural selection, and genetic drift, comment on the likelihood of adaptation to environmental change for species that have small population sizes versus species with large population sizes. At a minimum, a fully correct answer will incorporate all three of these processes into the answer.

When F_ST ≈ 0, a population

Which of the following statements is/are supported by the figure?

The graph below shows results of two simulations, both depicting the rise in frequency of a beneficial allele in a population of infinite size. The selection coefficient and the starting frequency are the same, but in one simulation the beneficial allele is dominant and in the other it is recessive. Neither allele is fixed by 500 generations. (a) Which simulation shows results for a dominant and which shows results for a recessive allele? How can you tell? (b) Neither of the alleles reaches fixation by 500 generations. If given enough time, will both of these alleles reach fixation in the population? Why or why not?

Lively and Dybdahl studied parasite infection rates in a population of asexual clonal snails. The graph below shows relative infection rates for the four most common clone genotypes and for several rare genotypes (all lumped together). Based on these data, they hypothesized that parasites adapted to infecting the most common clone genotypes in the population, and thus these genotypes had lower fitness. This is consistent with ________ operating in the population. Further evidence would be provided if ________.

Some Drosophila melanogaster larvae use a "sitting" foraging strategy in which they feed more or less in the same location, while "rovers" wander around the substrate looking for more food sources. In the graph below, the dotted line corresponds to sitters and the solid line corresponds to rovers. This is an example of _______; over time we expect ________.