AP Bio Unit 6

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.

D

With what other idea of his time was Cuvier's theory of catastrophism most in conflict? A) the scala naturae B) the fixity of species C) island biogeography D) uniformitarianism

D

Which of Darwin's ideas had the strongest connection to his reading of Malthus's essay on human population growth? A) descent with modification B) variation among individuals in a population C) struggle for existence D) that the ancestors of the Galápagos finches had come from the South American mainland

C

A biologist doing a long-term study on a wild spider population observes increased variation in silk thickness. Which of the following could the spider population be experiencing? A) directional selection B) genetic drift C) stabilizing selection D) disruptive selection

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

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

D

In some jacana species, males take care of the eggs and young, and females compete among themselves for territories that contain one to several males. Female jacanas are significantly larger than males. Which of these statements would you predict to be true of this bird species? 1. Male jacana fitness is primarily limited by ability to take care of eggs and raise young. 2. Female jacana fitness is limited by the number of males in her territory with which a female mates. 3. Variation in reproductive success should be greater in male jacanas than in females. 4. Variation in reproductive success should be greater in female jacanas than in males. 5. Males and females have equal variation in reproductive success.

1,2, and 4

A population of organisms will not evolve if _____. A) all individual variation is due only to environmental factors B) the environment is changing at a relatively slow rate C) the population size is large D) the population lives in a habitat without competing species present

A

Given what we know about evolutionary biology, we expect to find the largest number of endemic species in which of the following geological features, which have existed for at least a few million years? A) an isolated ocean island in the tropics B) an extensive mountain range C) a grassland in the center of a large continent, with extreme climatic conditions D) a shallow estuary on a warm-water coast

A

If Darwin had been aware of genes and their typical mode of transmission to subsequent generations, with which statement would he most likely have been in agreement? A) If natural selection can change gene frequency in a population over generations, given enough time and genetic diversity, then natural selection can cause sufficient genetic change to produce new species from old ones. B) If an organism's somatic cell genes change during its lifetime, making it more fit, then it will be able to pass these genes on to its offspring. C) If an organism acquires new genes by engulfing, or being infected by, another organism, then a new genetic species will result. D) A single mutation in a single gene in a single gamete, if inherited by future generations, will produce a new species.

A

In 1983 a population of dark-eyed junco birds became established on the campus of the University of California, San Diego (UCSD), which is located many miles from the junco's normal habitat in the mixed-coniferous temperate forests in the mountains. Juncos have white outer tail feathers that the males display during aggressive interactions and during courtship displays. Males with more white in their tail are more likely to win aggressive interactions, and females prefer to mate with males with more white in their tails. Females have less white in their tails than do males, and display it less often. (Pamela J. Yeh. 2004. Rapid evolution of a sexually selected trait following population establishment in a novel habitat. Evolution 58[1]:166-74.) 35) Refer to the paragraph on dark-eyed junco birds. The UCSD campus male junco population tails are about 36% white, whereas the tails of males from nearby mountain populations are about 40-45% white. The founding stock of UCSD birds was likely from the nearby mountain populations because some of those birds overwinter on the UCSD campus each year. Population sizes on the UCSD campus have been reasonably large, and there are significant habitat differences between the UCSD campus and the mountain coniferous forests; UCSD campus has a more open environment (making birds more visible) and a lower junco density (decreasing intraspecific competition) than that in the mountain forests. Given this information, which of the following evolutionary mechanisms do you think is most likely responsible for the difference between the UCSD and mountain populations? A) natural selection B) genetic drift C) gene flow D) mutation

A

Mutation is the only evolutionary mechanism that _____. A) does little to change allele frequencies B) is more important in eukaryotes than in prokaryotes C) happens in all populations D) has no effect on genetic variation

A

One out of 10,000 babies born in North America is affected by cystic fibrosis, a recessive condition. Assuming that the North American human population is in Hardy-Weinberg equilibrium for this trait, what percentage of the population is heterozygous for this trait? (Remember the equation for a population in Hardy-Weinberg equilibrium: p2 + 2pq + q2 = 1.) A) 2% B) 1% C) 0.01%

A

Over time, the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasing _____. A) gene flow B) genetic drift C) geographic isolation D) nonrandom mating

A

Researchers discovered that a new strain of bacteria that cause tuberculosis (M. tuberculosis) taken from a dead patient has a point mutation in the rpoB gene that codes for part of the RNA polymerase enzyme. This mutant form of RNA polymerase does not function as well as the more common form of RNA polymerase. A commonly used antibiotic called rifampin does not affect the mutant rpoB bacteria. A researcher mixes M. tuberculosis with and without the rpoB mutation and adds the bacteria to cell cultures. Half the cell cultures contain only standard nutrients, while the other half of the cell cultures contain rifampin and the standard nutrients. After many cell generations, the researcher finds that _____. A) very few M. tuberculosis in the standard nutrient cell cultures carry the rpoB gene mutation, but almost all of the M. tuberculosis in the cell cultures with rifampin carry the rpoB mutation B) almost all M. tuberculosis in the standard nutrient cell cultures carry the rpoB gene mutation, but very few of the M. tuberculosis in the cell cultures with rifampin carry the rpoB mutation C) very few M. tuberculosis in any of the cell cultures carry the rpoB gene mutation D) almost all of the M. tuberculosis in both types of cell cultures carry the rpoB mutation

A

Starting from the wild mustard Brassica oleracea, breeders have created the strains known as Brussels sprouts, broccoli, kale, and cabbage. Therefore, which of the following statements is correct? A) In this wild mustard, there is enough heritable variation to permit these different varieties. B) Heritable variation is low in wild mustard—otherwise this wild strain would have different characteristics. C) Natural selection is rare in wild populations of wild mustard. D) In wild mustard, most of the variation is due to differences in soil or other aspects of the environment.

A

Suppose 64% of a remote mountain village can taste phenylthiocarbamide (PTC) and must, therefore, have at least one copy of the dominant PTC taster allele. If this population conforms to Hardy-Weinberg expectations for this gene, what percentage of the population must be heterozygous for this trait? A) 48% B) 32% C) 16% D) 40%

A

The Dunkers are a religious group that moved from Germany to Pennsylvania in the mid-1700s. They do not marry with members outside their own immediate community. Today, the Dunkers are genetically unique and differ in gene frequencies, at many loci, from all other populations including those in their original homeland. Which of the following likely explains the genetic uniqueness of this population? A) founder effect and genetic drift B) population bottleneck and Hardy-Weinberg equilibrium C) heterozygote advantage and stabilizing selection D) mutation and natural selection

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) Resistance to DDT evolved in some fruit flies in order to allow them to survive. C) Alleles for DDT resistance arose by mutation during the period of DDT use because of selection for pesticide resistance.

A

The inability of organisms to evolve anything that could be an advantage reflects _____. A) the limits of historical constraints B) the inability to compromise C) the consequences of random mutations D) the consequences of inbreeding

A

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. In the United States, the parasite that causes malaria is not present, but African-Americans whose ancestors were from equatorial Africa are present. What should be happening to the sickle-cell allele in the United States, and what should be happening to it in equatorial Africa? A) directional selection; stabilizing selection B) directional selection; disruptive selection C) disruptive selection; stabilizing selection D) stabilizing selection; disruptive selection

A

Which statement correctly describes the role of chance in evolution? A) The ultimate source of new alleles is mutation, random changes in the nucleotide sequences of an organism's DNA. B) Evolution by natural selection proceeds by an accumulation of changes that occur by chance. C) An allele that increases evolutionary fitness cannot be lost from a population by chance events.

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

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

B

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

B

About thirteen different species of finches inhabit the Galápagos Islands today, all descendants of a common ancestor from the South American mainland that arrived a few million years ago. Genetically, there are four distinct lineages, but the thirteen species are currently classified among three genera. The first lineage to diverge from the ancestral lineage was the warbler finch (genus Certhidea). Next to diverge was the vegetarian finch (genus Camarhynchus), followed by five tree finch species (also in genus Camarhynchus) and six ground finch species (genus Geospiza). If the six ground finch species have evolved most recently, then which of these is the most logical prediction? A) They should be limited to the six islands that most recently emerged from the sea. B) Their genomes should be more similar to each other than are the genomes of the five tree finch species. C) They should share fewer anatomical homologies with each other than they share with the tree finches. D) The chances of hybridization between two ground finch species should be less than the chances of hybridization between two tree finch species.

B

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 _____. A) stabilizing selection was occurring in these species concerning larynx size B) sexual dimorphism was evolving over time in these species C) intrasexual selection seems to have occurred in both species D) selection was acting more directly upon genotype than upon phenotype

B

Catastrophism was Cuvier's attempt to explain the existence of _____. A) evolution B) the fossil record C) uniformitarianism D) the origin of new species

B

Identify the pair of homologous structures. A) Maple leaf and maple seed B) Maple leaf and oak leaf C) Neither of the above; plants do not have homologous structures.

B

If the bacterium Staphylococcus aureus experiences a cost for maintaining one or more antibiotic-resistance genes, what would happen in environments that lack antibiotics? A) These genes would be maintained in case the antibiotics appear. B) These bacteria would be outcompeted and replaced by bacteria that have lost these genes. C) These bacteria would try to make the cost worthwhile by locating and migrating to microenvironments where traces of antibiotics are present. D) The number of genes conveying antibiotic resistance would increase in these bacteria.

B

In 1959, doctors began using the powerful antibiotic methicillin to treat infections of Staphylococcus aureus, but within two years, methicillin-resistant strains of S. aureus (MRSA) appeared. How did the resistant strains of S. aureus emerge? A) In response to treatment of Staphylococcus aureus infections with methicillin, some bacteria began to synthesize cell walls using a protein that was not affected by methicillin. These bacteria survived the methicillin treatments and reproduced at higher rates than did other individuals. Over time, these resistant individuals became increasingly common. B) Staphylococcus aureus bacteria that were able to synthesize cell walls using a protein that was not affected by methicillin survived the methicillin treatments and reproduced at higher rates than did other individuals. Over time, these resistant individuals became increasingly common. C) In response to treatment of Staphylococcus aureus infections with methicillin, bacterial populations gradually began to synthesize cell walls using a protein that was not affected by methicillin.

B

In 1986, a nuclear power accident in Chernobyl, USSR (now Ukraine), led to high radiation levels for miles surrounding the plant. The high levels of radiation caused elevated mutation rates in the surviving organisms, and evolutionary biologists have been studying rodent populations in the Chernobyl area ever since. Based on your understanding of evolutionary mechanisms, which of the following most likely occurred in the rodent populations following the accident? A) Mutation caused genetic drift and decreased fitness. B) Mutation led to increased genetic variation. C) Mutation caused the fixation of new alleles. D) Mutations caused major changes in rodent physiology over time.

B

In the mid-1900s, the Soviet geneticist Lysenko believed that his winter wheat plants, exposed to increasingly colder temperatures, would eventually give rise to more cold-tolerant winter wheat. Lysenko's attempts in this regard were most in agreement with the ideas of _____. A) Cuvier B) Lamarck C) Darwin D) Lyell

B

Members of two different species possess a similar-looking structure that they use in a similar way to perform about the same function. Which of the following would suggest that the relationship more likely represents homology instead of convergent evolution? A) The two species live at great distance from each other. B) The two species share many proteins in common, and the nucleotide sequences that code for these proteins are almost identical. C) The structures in adult members of both species are similar in size. D) Both species are well adapted to their particular environments.

B

Rank the following one-base point mutations (from most likely to least likely) with respect to their likelihood of affecting the structure of the corresponding polypeptide. 1. insertion mutation deep within an intron 2. substitution mutation at the third position of an exonic codon 3. substitution mutation at the second position of an exonic codon 4. deletion mutation within the first exon of the gene A) 1, 2, 3, 4 B) 4, 3, 2, 1 C) 2, 1, 4, 3 D) 3, 1, 4, 2

B

Soon after the island of Hawaii rose above the sea surface (somewhat less than one million years ago), the evolution of life on this new island should have been most strongly influenced by _____. A) habitat differentiation B) the founder effect C) a genetic bottleneck D) sexual selection

B

The greatest number of endemic species is expected in environments that are _____. A) easily reached and ecologically diverse B) isolated and show little ecological diversity C) isolated and ecologically diverse D) easily reached and show little ecological diversity

B

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 _____. A) neutral variation B) frequency-dependent selection C) evolutionary imbalance D) heterozygote advantage

B

What must be true of any organ described as vestigial? A) It must be analogous to some feature in an ancestor. B) It must be homologous to some feature in an ancestor. C) It must be both homologous and analogous to some feature in an ancestor. D) It need be neither homologous nor analogous to some feature in an ancestor.

B

Which of the following represents an idea that Darwin learned from the writings of Thomas Malthus? A) Technological innovation in agricultural practices will permit exponential growth of the human population into the foreseeable future. B) Populations tend to increase at a faster rate than their food supply normally allows. C) Earth changed over the years through a series of catastrophic upheavals. D) The environment is responsible for natural selection.

B

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) nucleotide variability B) average heterozygosity C) geographic variability D) average number of loci

B

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 estimated frequency of allele A in the gene pool? A) 0.75 B) 0.125 C) 0.50 D) 0.25

C

Cotton-topped tamarins are small primates with tufts of long white hair on their heads. While studying these creatures, you notice that males with longer hair get more opportunities to mate and father more offspring. To test the hypothesis that having longer hair is adaptive in these males, you should _____. A) test whether other traits in these males are also adaptive B) look for evidence of hair in ancestors of tamarins C) determine if hair length is heritable D) test whether males with shaved heads are still able to mate

C

Cystic fibrosis is a genetic disorder in homozygous recessives that causes death during the teenage years. If 9 in 10,000 newborn babies have the disease, what are the expected frequencies of the dominant (A1) and recessive (A2) alleles according to the Hardy-Weinberg model? A) f(A1) = 0.9604, f(A2) = 0.0392 B) f(A1) = 0.9800, f(A2) = 0.0200 C) f(A1) = 0.9700, f(A2) = 0.0300 D) f(A1) = 0.9997, f(A2) = 0.0003

C

DDT was once considered a "silver bullet" that would permanently eradicate insect pests. Instead, DDT is largely useless against many insects. Which of these would have prevented this evolution of DDT resistance in insect pests? A) All habitats should have received applications of DDT at about the same time. B) The frequency of DDT application should have been higher. C) None of the insect pests would have genetic variations that resulted in DDT resistance. D) DDT application should have been continual.

C

Darwin and Wallace's theory of evolution by natural selection was revolutionary because it _____. A) was the first theory to refute the ideas of special creation B) proved that individuals acclimated to their environment over time C) dismissed the idea that species are constant and emphasized the importance of variation and change in populations D) was the first time a biologist had proposed that species changed through time

C

For a biologist studying a small fish population in the lab, which Hardy-Weinberg condition is easiest to meet? A) no genetic drift B) no selection C) no gene flow D) no mutation

C

On the Bahamian island of Andros, mosquitofish populations live in various, now-isolated, freshwater ponds that were once united. Currently, some predator-rich ponds have mosquitofish that can swim in short, fast bursts; other predator-poor ponds have mosquitofish that can swim continuously for a long time. When placed together in the same body of water, the two kinds of female mosquitofish exhibit exclusive breeding preferences. 44) If one builds a canal linking a predator-rich pond to a predator-poor pond, then what type(s) of selection should subsequently be most expected among the mosquitofish in the original predator-rich pond, and what type(s) should be most expected among the mosquitofish in the formerly predator-poor pond? A) stabilizing selection; directional selection B) stabilizing selection; stabilizing selection C) less-intense directional selection; more-intense directional selection D) less-intense disruptive selection; more-intense disruptive selection

C

Parasitic species tend to have simple morphologies. Which of the following statements best explains this observation? A) Parasites are lower organisms, and this is why they have simple morphologies. B) Parasites do not live long enough to inherit acquired characteristics. C) Simple morphologies convey some advantage in most parasites. D) Parasites have not yet had time to progress, because they are young evolutionarily.

C

The cow Bos primigenius (which is bred for meat and milk) has a smaller brain and larger eyes than closely related wild species of ungulates. These traits most likely arose by _____. A) natural selection, because these traits evolved in the population over time B) natural selection, because these traits were not consciously selected by humans C) artificial selection, because changes in these traits co-occurred with human selection for high milk output and high muscle content D) artificial selection, because these animals differ from their close relatives and common ancestor

C

The role that humans play in artificial selection is to _____. A) determine who lives and who dies B) create genetic diversity C) choose which organisms reproduce D) perform artificial insemination

C

Which of these conditions are always true of populations evolving due to natural selection? Condition 1: The population must vary in traits that are heritable. Condition 2: Some heritable traits must increase reproductive success. Condition 3: Individuals pass on most traits that they acquire during their lifetime. A) Condition 1 only B) Condition 2 only C) Conditions 1 and 2 D) Conditions 2 and 3

C

You read about soapberry bugs and select the correct statement describing relative fitness in these individuals. A) A soapberry bug with high relative fitness feeds more successfully on fruits than do other bugs. B) A soapberry bug with high relative fitness has more mates than other bugs. C) A soapberry bug with high relative fitness has a relatively high number of offspring that survive to reproductive age.

C

A farmer uses triazine herbicide to control pigweed in his field. For the first few years, the triazine works well and almost all the pigweed dies; but after several years, the farmer sees more and more pigweed. Which of these explanations best explains what happened? A) The herbicide company lost its triazine formula and started selling poor-quality triazine. B) Natural selection caused the pigweed to mutate, creating a new triazine-resistant species. C) Triazine-resistant pigweed has less-efficient photosynthesis metabolism. D) Triazine-resistant weeds were more likely to survive and reproduce.

D

For biologists studying a large flatworm population in the lab, which Hardy-Weinberg condition is most difficult to meet? A) no selection B) no genetic drift C) no gene flow D) no mutation

D

HIV's genome of RNA includes the code for reverse transcriptase (RT), an enzyme that acts early in infection to synthesize a DNA genome off of an RNA template. The HIV genome also codes for protease (PR), an enzyme that acts later in infection by cutting long viral polyproteins into smaller, functional proteins. Both RT and PR represent potential targets for antiretroviral drugs. Drugs called nucleoside analogs (NA) act against RT, whereas drugs called protease inhibitors (PI) act against PR. Every HIV particle contains two RNA molecules. If two genes from one RNA molecule become detached and then, as a unit, get attached to one end of the other RNA molecule within a single HIV particle, which of these is true? A) There are now fewer genes within the viral particle. B) There are now more genes within the viral particle. C) A point substitution mutation has occurred in the retroviral genome. D) One of the RNA molecules has experienced gene duplication as the result of translocation.

D

HIV's genome of RNA includes the code for reverse transcriptase (RT), an enzyme that acts early in infection to synthesize a DNA genome off of an RNA template. The HIV genome also codes for protease (PR), an enzyme that acts later in infection by cutting long viral polyproteins into smaller, functional proteins. Both RT and PR represent potential targets for antiretroviral drugs. Drugs called nucleoside analogs (NA) act against RT, whereas drugs called protease inhibitors (PI) act against PR. Which of the following represents the treatment option most likely to avoid the evolution of drug-resistant HIV (assuming no drug interactions or side effects)? A) using a series of NAs, one at a time, and changed about once a week B) using a single PI, but slowly increasing the dosage over the course of a week C) using high doses of NA and a PI at the same time for a period not to exceed one day D) using moderate doses of NA and two different PIs at the same time for several months

D

In 1983 a population of dark-eyed junco birds became established on the campus of the University of California, San Diego (UCSD), which is located many miles from the junco's normal habitat in the mixed-coniferous temperate forests in the mountains. Juncos have white outer tail feathers that the males display during aggressive interactions and during courtship displays. Males with more white in their tail are more likely to win aggressive interactions, and females prefer to mate with males with more white in their tails. Females have less white in their tails than do males, and display it less often. (Pamela J. Yeh. 2004. Rapid evolution of a sexually selected trait following population establishment in a novel habitat. Evolution 58[1]:166-74.) 34) Refer to the paragraph on dark-eyed junco birds. The UCSD campus male junco population tails were, on average, 36% white, whereas the tails of males from nearby mountain populations averaged 40-45% white. If this observed trait difference were due to a difference in the original colonizing population, it would most likely be due to _____. A) mutations in the UCSD population B) gene flow between populations C) a genetic bottleneck D) a founder effect

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) 0.64 B) 0.75 C) 0.36 D) 0.80

D

Many crustaceans (for example, lobsters, shrimp, and crayfish) use their tails to swim, but crabs have reduced tails that curl under their shells and are not used in swimming. This is an example of _____. A) convergent evolution B) a homologous structure C) natural selection D) a vestigial trait

D

Of the following anatomical structures, which is homologous to the bones in the wing of a bird? A) bones in the hind limb of a kangaroo B) chitinous struts in the wing of a butterfly C) bony rays in the tail fin of a flying fish D) bones in the flipper of a whale

D

Pseudogenes are _____. A) composed of RNA, rather than DNA B) the same things as introns C) unrelated genes that code for the same gene product D) nonfunctional vestigial genes

D

The higher the proportion of loci that are "fixed" in a population, the lower are that population's _____. A) nucleotide variability B) chromosome number C) average heterozygosity D) nucleotide variability and average heterozygosity

D

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.

D

When imbalances occur in the sex ratio of sexual species that have two sexes (that is, other than a 50:50 ratio), the members of the minority sex often receive a greater proportion of care and resources from parents than do the offspring of the majority sex. This is most clearly an example of _____. A) sexual selection B) balancing selection C) stabilizing selection D) frequency-dependent selection

D

Which of the following scientists argued that variation among individuals allows evolution to occur? A) Aristotle B) Lamarck C) Linnaeus D) Wallace

D