Exam 20: Mechanisms of Evolution

In a population of 200 individuals at Hardy-Weinberg equilibrium, 72 are homozygous recessive for the character of eye color (cc).One hundred individuals from this population die from a fatal disease.Thirty-six of the survivors are homozygous recessive.In the new population, the frequency of the dominant allele is

Draw a graph showing how the frequency of heterozygotes in a population would vary depending on the frequency of the alleles in the population, assuming Hardy-Weinberg equilibrium.

Which observation from Darwin's stay in the Galápagos Islands was most instrumental toward his eventual development of evolutionary theory?

The ultimate origin of genetic variation is

Which mode(s) of selection arise(s) when individuals at both extremes of the distribution have high fitness?

Individuals who carry two copies of the sickle allele of a gene for hemoglobin suffer from a usually fatal anemia.However, individuals who carry one sickle allele have a greater resistance to malaria.Such individuals demonstrate the principle of _______, which accounts for the maintenance of both the normal and the sickle alleles.

A population of monkeyflowers has 39 individuals that are BB at a locus, 42 that are Bb, and 19 that are bb.This population has _______ fewer heterozygotes than would be expected under Hardy‒Weinberg equilibrium.

Selection currently maintains an intermediate body size in a population of salmon.Bears selectively prey on the largest individuals, while smaller individuals produce fewer offspring because they have difficulty competing with the larger individuals.Suppose that the food supply increased, reducing the competition among the salmon for food.Most likely, the salmon size would decrease due to _______ selection.

Which statement about mutations is false?

Which of the following is not an example of adaptation?

The average survival rates of individuals of different sizes in a mouse population were assayed and are presented in the table. Assume that body size is at least partially heritable.Assuming that all other aspects are independent of size, this population is most likely experiencing _______ selection, and the variation in the population should _______ over many generations.

Due to various causes, including DDT poisoning, the population size of whooping cranes was reduced to about a dozen during the 1970s.The population size has since rebounded, and there are now hundreds of whooping cranes.Which feature would not be expected in the current populations of whooping cranes?

Charles Darwin and _______ independently articulated the concept of natural selection.

Suppose a population of flour beetles has 1,000 individuals.Normally the beetles are red; however, this population is polymorphic for a mutant autosomal body color, black, designated by bb.Red is dominant to black, so BB and Bb genotypes are red.Assume the population is at Hardy-Weinberg equilibrium, with equal frequencies of the two alleles.What would be the allele frequencies if a population bottleneck occurred and only four individuals survived: one female red heterozygote and three black males?

Suppose variants at a single locus affect wing length in a species of crickets, with homozygotes for the L allele having long wings, homozygotes for the l allele having short wings, and heterozygotes having wings of intermediate length.In one population of 500 individuals, 340 have long wings, 120 have intermediate-length wings, and 40 have short wings.The frequency of the L allele is _______.

In Drosophila melanogaster, body size increases as the distance from the equator increases, at least partly because of genetic differences.Population geneticists refer to such a geographical pattern as _______.

A small population of sawflies that was once connected to a larger population but is now isolated is no longer experiencing

Which is not a mechanism for maintaining genetic variation in populations?

In a population of pitcher plants, 200 individuals are sampled for variation at a locus.Sixteen are heterozygous for the X1 allele, and four are homozygous for it.What is the frequency of the X1 allele?

Which statement about fitness and natural selection is true?