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Exam 21: The Evolution of Populations

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Question 21

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Which process in sexual reproduction results in diversity at the nucleotide level?

A) chromosome shuffling
B) chromosome crossover
C) independent assortment of chromosomes
D) random distribution of chromosomes

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Question 22

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Which one of the genetic drift effects would limit natural selection?

A) allele frequencies change at random
B) loss of genetic variation
C) cause harmful alleles to be fixed
D) alter frequencies in small population

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Question 23

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Please use the following information to answer the question(s) below. In those parts of equatorial Africa where the malaria parasite is most common, the sickle-cell allele constitutes 20% of the β hemoglobin alleles in the human gene pool. -With respect to the sickle-cell allele, what should be true of the β hemoglobin locus in U.S. populations of African-Americans whose ancestors were from equatorial Africa? 1) The average heterozygosity at this locus should be decreasing over time. 2) There is an increasing heterozygote advantage at this locus. 3) Diploidy is helping to preserve the sickle-cell allele at this locus. 4) Frequency-dependent selection is helping to preserve the sickle-cell allele at this locus.

Please use the following information to answer the question(s) below. In those parts of equatorial Africa where the malaria parasite is most common, the sickle-cell allele constitutes 20% of the β hemoglobin alleles in the human gene pool. -Although selection is clearly present, if the ideal equilibrium of alleles existed, what should be the proportion of heterozygous individuals in populations that live here?

Which of the following statements best summarizes evolution as it is viewed today?

Which statement about the beak size of finches on the island of Daphne Major during prolonged drought is true?

Identify the statement that describes the imperfection of natural selection.

What is true of natural selection?

Most Swiss starlings produce four to five eggs in each clutch. Starlings producing fewer, or more, than this have reduced fitness. Which of the following terms best describes this situation?

In peas, a gene controls flower color such that R = purple and r = white. In an isolated pea patch, there are 36 purple-flowering plants and 64 white-flowering plants. Assuming Hardy-Weinberg equilibrium, what is the value of q for this population?

Please use the following information to answer the question(s) below. A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive trait (aa) , the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants. -What is the most reasonable conclusion that can be drawn from the fact that the frequency of the recessive trait (aa) has not changed over time?

The same gene that causes various coat patterns in wild and domesticated cats also causes a cross-eyed condition in these cats, the cross-eyed condition being slightly maladaptive. In a hypothetical environment, the coat pattern that is associated with crossed eyes is highly adaptive, with the result that both the coat pattern and the cross-eyed condition increase in a feline population over time. Which statement is supported by these observations?

Use Figure 21.2 to answer the following question. Figure 21.2 Soon after the island of Hawaii rose above the sea surface (somewhat less than 1 million years ago) , the evolution of life on this new island should have been most strongly influenced by

Please use the following information to answer the question(s) below. You are studying three populations of birds. Population A has 10 birds, of which 1 is brown (a recessive trait) and 9 are red. Population B has 100 birds, of which 10 are brown. Population C has 30 birds, and 3 of them are brown. -Which population is most likely to be subject to the bottleneck effect?

The restriction enzymes of bacteria protect the bacteria from successful attack by bacteriophages, whose genomes can be degraded by the restriction enzymes. The bacterial genomes are not vulnerable to these restriction enzymes because bacterial DNA is methylated. This situation selects for bacteriophages whose genomes are also methylated. As new strains of resistant bacteriophages become more prevalent, this in turn selects for bacteria whose genomes are not methylated and whose restriction enzymes instead degrade methylated DNA. The outcome of the conflict between bacteria and bacteriophage at any point in time results from

How can genetic variation at the whole gene level (gene variability) be quantified?

Which of the following describes a mechanism for generating more genes?

The frequency of individuals born in a population with PKU is q2. There is one PKU (q2) birth per 10,000 births. The frequency of the recessive allele for PKU in this population is q = 0.01. The frequency of the dominant allele in this population is p = 1 - q = 0.99. What is the frequency of carriers (2pq) in this population?

Please use the following information to answer the question(s) below. In the year 2500, five male space colonists and five female space colonists (all unrelated to each other) settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring randomly mate for generations. All 10 of the original colonists had free earlobes, and 2 were heterozygous for that trait. The allele for free earlobes is dominant to the allele for attached earlobes. -Swine are vulnerable to infection by bird flu virus and human flu virus, which can both be present in an individual pig at the same time. When this occurs, it is possible for genes from bird flu virus and human flu virus to be combined. If the human flu virus contributes a gene for Tamiflu resistance (Tamiflu is an antiviral drug) to the new virus, and if the new virus is introduced to an environment lacking Tamiflu, then what is most likely to occur?

Adult male humans generally have deeper voices than do adult female humans, which is the direct result of higher levels of testosterone causing growth of the larynx. If the fossil records of apes and humans alike show a trend toward decreasing larynx size in adult females and increasing larynx size in adult males, then