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Problem 1
In what sense is the Hardy–Weinberg principle a null hypothesis?
Problem 2
Why isn't inbreeding considered an evolutionary process?
a. It does not change genotype frequencies.
b. It does not change allele frequencies.
c. It does not occur often enough to be important in evolution.
d. It does not violate the assumptions of the Hardy–Weinberg principle.
Problem 3
Why is genetic drift aptly named? Select True or False for each statement.
T/F It causes allele frequencies to drift up or down randomly.
T/F It occurs when alleles from one population drift into another.
T/F It occurs when mutations drift into a genome.
Problem 4
True or false? Gene flow can either increase or decrease the average fitness of a population. Explain.
Problem 5
In a population of 2500, how many babies would you expect to have cystic fibrosis, a homozygous recessive condition, if the frequency of the dominant allele is 0.9 and the population is at Hardy–Weinberg equilibrium?
a. 0.9 × 2500 = 2250
b. 2 × 0.9 × 0.1 × 2500 = 450
c. 0.9 × 0.1 × 2500 = 225
d. 0.1 x 0.1 x 2500 = 25
Problem 6
In the 1700s and 1800s, royalty in Europe often married their close relatives; furthermore, recessive genetic diseases such as hemophilia showed up much more often among royals than in the general population. Explain the likely connection.
- Determine what is incorrect in the following statement: Red deer mutated their genes so that they could have larger antlers to compete for mates.
Problem 7
Problem 7
Determine what is incorrect in the following statement: Deer mice living on beaches mutated their genes so that they could have white fur color, providing better camouflage to survive on beaches.
Problem 8
Draw a small concept map showing how selection, genetic drift, gene flow, and mutation relate to genetic variation.
- In humans, albinism is caused by loss-of-function mutations in genes involved in the synthesis of melanin, the dark pigment in skin. Only people homozygous for a loss-of-function allele (genotype aa) have the albino phenotype. In Americans of northern European ancestry, albino individuals are present at a frequency of about 1 in 10,000 (or 0.0001). Assuming that genotypes are in Hardy–Weinberg equilibrium, what is the predicted frequency of Caucasians in the United States who carry a single allele for albinism?
Problem 9
- Suppose you were studying several species of monkeys. In one, males never helped females raise offspring. In another, males provided just as much parental care as females except for actually carrying the fetus during pregnancy. How does the fundamental asymmetry of sex compare in the two species? How would you expect sexual dimorphism to compare between the two species?
Problem 10
Problem 11
Human activities are causing the fragmentation of the Brazilian Atlantic rain forest. One result is that toucans have become extinct or nearly extinct in some of the forest fragments. Does the absence of toucans affect the forest?
Toucans disperse seeds of key forest species such as juçara palms by eating the fruit and defecating the seeds in new locations, sometimes more than a kilometer away. If there are no toucans, is the genetic diversity of palms likely to increase or decrease within forest fragments? Why?
a. Increase (due to increased genetic drift)
b. Decrease (due to decreased gene flow)
c. Decrease (due to decreased mutation rate)
d. Decrease (due to decreased natural selection)
Problem 12
Human activities are causing the fragmentation of the Brazilian Atlantic rain forest. One result is that toucans have become extinct or nearly extinct in some of the forest fragments. Does the absence of toucans affect the forest? Toucans can eat fruits with large seeds because their large bills can open wide. Most other birds in the same forest can only eat small seeds. Ecologist Mauro Galetti and his colleagues measured the seed sizes of palms in forest fragments with and without toucans. The graphs show two of the forest populations they studied. What is the take-home message of the data?
