BIOL 1202 Chapter 23

A trend toward the decrease in the size of plants on the slopes of mountains as altitudes increase is an example of A) a cline. B) a bottleneck. C) relative fitness. D) genetic drift. E) geographic variation.

A

Allele frequencies in a gene pool may shift randomly and by chance. What is this random shift called? A) Genetic drift B) directional selection C) Gene flow

A

Blue poppies native to China were grown at a plant-breeding center in California. The plants with the thickest leaves were most likely to survive and reproduce in the drier climate. After several generations, the percentage of thick-leaved plants had increased by 42%. This adaptation of the poppies to their new environment is due to _____. A) neutral variation B) directional selection C) genetic drift D) stabilizing selection E) disruptive selection

B

Crossing over, resulting in an increase in genetic variation, occurs between _____. A) sister chromatids of homologous chromosomes B) nonsister chromatids of homologous chromosomes C) sex cells and somatic cells D) nonsister chromatids of nonhomologous chromosomes E) sister chromatids of nonhomologous chromosomes

B

Every few years a giant axe chops off the head of every person who is over 6 feet tall. How will this affect the human population? A) Gene flow will increase. B) Alleles that promote "tallness" will decrease in frequency. C) The mutation rate will increase. D) Genetic drift will play less of a role in the evolution of humans. E) It will increase in number since shorter people use fewer resources than taller people.

B

Heterozygote advantage should be most closely linked to which of the following? A) sexual selection B) stabilizing selection C) random selection D) directional selection E) disruptive selection

B

Homologous pairs of chromosomes are lined up independently of other such pairs during _____. A) metaphase II B) metaphase I C) anaphase I D) prophase II E) telophase II

B

In the formula for determining a population's genotype frequencies, the 2 in the term 2pq is necessary because A) the population is diploid. B) heterozygotes can come about in two ways. C) the population is doubling in number. D) heterozygotes have two alleles.

B

Rabbit ear size tends to decrease as latitude increases. This is an example of _____. A) heterozygote advantage B) artificial selection C) polymorphism D) genetic drift E) a cline

E

What is the only evolutionary mechanism that consistently leads to adaptive evolution? A) gene flow B) the bottleneck effect C) genetic drift D) neutral variation E) natural selection

E

How does diploidy help to preserve genetic variation? A) It allows recessive alleles that may not be favored in the current environment to be preserved in the gene pool by propagation in heterozygotes. B) It allows the frequency of a recessive allele in a population to be predicted under certain conditions. C) It restricts the gene pool by chance events such as floods or other catastrophic events. D) It helps individual organisms make a greater contribution to the gene pool of the next generation. E) It fosters the exchange of genes between different populations.

A

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of the allele a is 0.3. What is the frequency of individuals that are homozygous for this allele? A) 0.09 B) 0.49 C) 0.9 D) 9.0

A

In evolutionary terms, an organism's fitness is measured by its _____. A) contribution to the gene pool of the next generation B) health C) stability in the face of environmental change D) genetic variability E) mutation rate

A

In human gamete production there is an average of _____ crossover events per chromosome pair. A) 2-3 B) 5-6 C) 0-1 D) 9-10 E) 10+

A

The fruit fly Drosophila melanogaster has an allele that confers resistance to DDT and similar insecticides. Laboratory strains of D. melanogaster have been established from flies collected in the wild in the 1930s (before the widespread use of insecticides) and the 1960s (after 20 years of DDT use). Lab strains established in the 1930s have no alleles for DDT resistance. In lab strains established in the 1960s, the frequency of the DDT-resistance allele is 37%. Which statement is correct? A) The evolutionary fitness associated with the heritable trait of DDT resistance changed once DDT use became widespread. B) Alleles for DDT resistance arose by mutation during the period of DDT use because of selection for pesticide resistance. C) Resistance to DDT evolved in some fruit flies in order to allow them to survive

A

There are those who claim that the theory of evolution cannot be true because the apes, which are supposed to be closely related to humans, do not likewise share the same large brains, capacity for complicated speech, and tool-making capability. They reason that if these features are generally beneficial, then the apes should have evolved them as well. Which of these provides the best argument against this misconception? A) Advantageous alleles do not arise on demand. B) A population's evolution is limited by historical constraints. C) Adaptations are often compromises. D) Evolution can be influenced by environmental change.

A

What situation most likely explains the occasional high frequency of certain inherited disorders among human populations established by a small population? A) founder effect B) nucleotide variability C) bottleneck effect D) mutation E) gene flow

A

Which of the following are basic components of the Hardy-Weinberg model? A) Frequencies of two alleles in a gene pool before and after many random matings B) Allele frequencies in a subset of the population C) Allele frequencies, number of individuals in the population D) Allele frequencies, phenotype frequencies

A

Which of the following evolutionary forces consistently results in adaptive changes in allele frequencies? A) Selection B) Inbreeding C) Mutation D) There is no evolutionary force that results in adaptive changes in allele frequencies.

A

Which variable is likely to undergo the largest change in value resulting from a mutation that introduces a new allele into a population at a locus for which all individuals formerly had been fully homozygous? A) average heterozygosity B) nucleotide variability C) geographic variability D) average number of loci

A

You are maintaining a small population of fruit flies in the laboratory by transferring the flies to a new culture bottle after each generation. After several generations, you notice that the viability of the flies has decreased greatly. Recognizing that small population size is likely to be linked to decreased viability, the best way to reverse this trend is to A) cross your flies with flies from another lab. B) reduce the number of flies that you transfer at each generation. C) transfer only the largest flies. D) change the temperature at which you rear the flies. E) shock the flies with a brief treatment of heat or cold to make them more hardy.

A

According to the Hardy-Weinberg theorem, the frequencies of alleles in a population will remain constant if _____ is the only process that affects the gene pool. A) mutation B) genetic drift C) immigration D) sexual selection E) sexual reproduction

E

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. A) 1 only B) 1 and 3 C) 2 and 3 D) 1, 2, and 3 E) 1, 2, and 4

B

Modern travel along with migration reduces the probability of _____ having an effect on the evolution of humans. A) disease B) genetic drift C) gene flow D) mutation E) natural selection

B

The ease with which humans travel across the globe is likely to increase _____. A) natural selection B) gene flow C) mutation D) genetic drift E) all of these

B

The evolutionary effects of genetic drift are greatest when _____. A) intraspecific competition is weak B) the population size is small C) the population size is large D) intraspecific competition is intense E) sexual selection occurs

B

What is the frequency of the A1A2 genotype in a population composed of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals? A) 80 B) 0.4 C) 0.5 D) 0.1

B

Which of the following evolutionary forces could create new genetic information in a population? A) Selection B) Mutation C) Genetic drift D) Nonrandom mating

B

Which of the following statements is not a part of the Hardy-Weinberg principle? A) When alleles are transmitted according to the rules of Mendelian inheritance, their frequencies do not change over time. B) The genotype frequencies in the offspring generation must add up to two. C) If allele frequencies in a population are given by p and q, then genotype frequencies will be given by p 2, 2pq, and q 2 for generation after generation. D) Even if allele A1 is dominant to allele A2 , it does not increase in frequency.

B

Which statement about the beak size of finches on the island of Daphne Major during prolonged drought is true? A) Each bird evolved a deeper, stronger beak as the drought persisted. B) Each bird's survival was strongly influenced by the depth and strength of its beak as the drought persisted. C) Each bird that survived the drought produced only offspring with deeper, stronger beaks than seen in the previous generation. D) The frequency of the strong-beak alleles increased in each bird as the drought persisted.

B

All the genes in a population are that population's _____. A) Hardy-Weinberg B) genotype C) gene pool D) fitness E) phenotype

C

Although each of the following has a better chance of influencing gene frequencies in small populations than in large populations, which one most consistently requires a small population as a precondition for its occurrence? A) mutation B) nonrandom mating C) genetic drift D) natural selection E) gene flow

C

Evolution A) must happen, due to organisms' innate desire to survive. B) must happen whenever a population is not well-adapted to its environment. C) can happen whenever any of the conditions for Hardy-Weinberg equilibrium are not met. D) requires the operation of natural selection. E) requires that populations become better suited to their environments.

C

If, on average, 46% of the loci in a species' gene pool are heterozygous, then the average homozygosity of the species should be A) 23%. B) 46%. C) 54%. D) There is not enough information to say.

C

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? A) artificial selection B) directional selection C) stabilizing selection D) disruptive selection E) sexual selection

C

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? A) The new virus will maintain its Tamiflu-resistance gene, just in case of future exposure to Tamiflu. B) The Tamiflu-resistance gene will undergo mutations that convert it into a gene that has a useful function in this environment. C) If the Tamiflu-resistance gene involves a cost, it will experience directional selection leading to reduction in its frequency. D) If the Tamiflu-resistance gene confers no benefit in the current environment, and has no cost, the virus will become dormant until Tamiflu is present.

C

What is the frequency of the A1 allele in a population composed of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals? A) 0.5 B) 0.7 C) 0.3 D) 0.1

C

Which of the following is a true statement concerning genetic variation? A) It is created by the direct action of natural selection. B) It arises in response to changes in the environment. C) It must be present in a population before natural selection can act upon the population. D) It tends to be reduced by the processes involved when diploid organisms produce gametes. E) A population that has a higher average heterozygosity has less genetic variation than one with a lower average heterozygosity.

C

A mutation occurs when _____. A) population sizes are small B) individuals leave a population C) individuals enter a population D) there is a change in the DNA sequence of a gene E) some individuals leave more offspring than other individuals

D

A proficient engineer can easily design skeletal structures that are more functional than those currently found in the forelimbs of such diverse mammals as horses, whales, and bats. The actual forelimbs of these mammals do not seem to be optimally arranged because A) natural selection has not had sufficient time to create the optimal design in each case, but will do so given enough time. B) in many cases, phenotype is not merely determined by genotype, but by the environment as well. C) though we may not consider the fit between the current skeletal arrangements and their functions excellent, we should not doubt that natural selection ultimately produces the best design. D) natural selection is generally limited to modifying structures that were present in previous generations and in previous species

D

Genetic drift is a process based on _____. A) emigration B) mutation C) differential reproductive success correlated to the relationship between a phenotype and the environment D) the role of chance E) immigration

D

How many of these statements regarding populations are true? 1. Mature males and females of a population can interbreed with each other. 2. Populations are sometimes geographically isolated from other populations. 3. Biological species are made up of populations. 4. Members of a population tend to be genetically more similar to each other than to members of other populations. 5. Populations have genomes, but not gene pools. A) Only one of these statements is true. B) Two of these statements are true. C) Three of these statements are true. D) Four of these statements are true. E) All five of these statements are true.

D

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.1. What is the frequency of individuals with AA genotype? A) 0.20 B) 0.32 C) 0.42 D) 0.81

D

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? A) 0.36 B) 0.64 C) 0.75 D) 0.80

D

In the wild, male house finches (Carpodus mexicanus) vary considerably in the amount of red pigmentation in their head and throat feathers, with colors ranging from pale yellow to bright red. These colors come from carotenoid pigments that are found in the birds' diets; no vertebrates are known to synthesize carotenoid pigments. Thus, the brighter red the male's feathers are, the more successful he has been at acquiring the red carotenoid pigment by his food-gathering efforts (all other factors being equal). During breeding season, one should expect female house finches to prefer to mate with males with the brightest red feathers. Which of the following is true of this situation? A) Alleles that promote more efficient acquisition of carotenoid-containing foods by males should increase over the course of generations. B) Alleles that promote more effective deposition of carotenoid pigments in the feathers of males should increase over the course of generations. C) There should be directional selection for bright red feathers in males. D) Three of the statements are correct. E) Two of the statements are correct.

D

Hardy-Weinberg equilibrium must occur in populations wherein A) an allele remains fixed. B) no genetic variation exists. C) natural selection is not operating. D) All three of the responses above are correct. E) Only two of the responses above are correct.

E

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. Over the course of evolutionary time, what should occur? A) Methylated DNA should become fixed in the gene pools of bacterial species. B) Nonmethylated DNA should become fixed in the gene pools of bacteriophages. C) Methylated DNA should become fixed in the gene pools of bacteriophages. D) Methylated and nonmethylated strains should be maintained among both bacteria and bacteriophages, with ratios that vary over time. E) Both the first and second responses are correct.

D

What genotype frequencies are expected under Hardy-Weinberg equilibrium for a population with allele frequencies of p = 0.8 and q = 0.2 for a particular gene? A) The expected genotype frequencies are 0.32, 0.64, and 0.04 for A1A1, A1A2 , and A2A2 , respectively. B) The expected genotype frequencies are 0.25, 0.5, and 0.25 for A1A1, A1A2 , and A2A2 , respectively. C) The expected genotype frequencies are 0.33, 0.33, and 0.33 for A1A1, A1A2 , and A2A2 , respectively. D) The expected genotype frequencies are 0.64, 0.32, and 0.04 for A1A1, A1A2 , and A2A2 , respectively.

D

What is true of natural selection? A) Natural selection is a random process. B) Natural selection creates beneficial mutations. C) The only way to eliminate harmful mutations is through natural selection. D) Mutations occur at random; natural selection can preserve and distribute beneficial mutations. E) Mutations occur when directed by the good of the species; natural selection edits out harmful mutations and causes populations to adapt to the beneficial mutations.

D

Which statement about variation is true? A) All phenotypic variation is the result of genotypic variation. B) All genetic variation produces phenotypic variation. C) All nucleotide variability results in neutral variation. D) All new alleles are the result of nucleotide variability. E) All geographic variation results from the existence of clines.

D

You sample a population of butterflies and find that 56% are heterozygous at a particular locus. What should be the frequency of the recessive allele in this population? A) 0.08 B) 0.09 C) 0.70 D) Allele frequency cannot be determined from this information.

D

True or false? The Hardy-Weinberg model makes the following assumptions: no selection at the gene in question; no genetic drift; no gene flow; no mutation; random mating.

True