Biology 2 Final

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1) 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) dismissed the idea that species are constant and emphasized the importance of variation and change in populations

2) Which of the following is the best modern definition of evolution?
A) descent with modification
B) change in the number of genes in a population over time
C) survival of the fittest
D) inheritance of acquired characters

A) descent with modification

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

E) bones in the flipper of a whale

4) Which of the following evidence most strongly supports the common origin of all life on Earth? All organisms _____.
A) require energy
B) use essentially the same genetic code
C) reproduce
D) show heritable variation
E) evolve

B) use essentially the same genetic code

5) If x indicates the location of fossils of two closely related species, then fossils of their most-recent common ancestor are most likely to occur in which stratum?
A) A
B) B
C) C
D) D

C

6) If x indicates the fossils of two closely related species, neither of which is extinct, then their remains may be found in how many of these strata?
A) one stratum
B) two strata
C) three strata
D) four strata

2

7) 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) Their genomes should be more similar to each other than are the genomes of the five tree finch species.

8) Logically, which of these should cast the most doubt on the relationships depicted by an evolutionary tree?
A) None of the organisms depicted by the tree ate the same foods.
B) Some of the organisms depicted by the tree had lived in different habitats.
C) The skeletal remains of the organisms depicted by the tree were incomplete (in other words, some bones were missing).
D) Transitional fossils had not been found.
E) Relationships between DNA sequences among the species did not match relationships between skeletal patterns.

E) Relationships between DNA sequences among the species did not match relationships between skeletal patterns.

9) Fossils of Thrinaxodon, a species that lived during the Triassic period, have been found in both South Africa and Antarctica. Thrinaxodon had a reptile-like skeleton and laid eggs, but small depressions on the front of its skull suggest it had whiskers and, therefore, fur. Thrinaxodon may have been warm-blooded. The fossils of Thrinaxodon are consistent with the hypothesis that _____.
A) fossils found in a given area look like the modern species in that same area
B) the environment where it lived was very warm
C) mammals evolved from a reptilian ancestor
D) Antarctica and South Africa separated after Thrinaxodon went extinct

C) mammals evolved from a reptilian ancestor

10) The Irish "elk" described by Georges Cuvier suggests that _____.
A) organisms could not have originated by special creation
B) organisms could go extinct
C) the great flood or some other catastrophe caused the evolution of new species
D) the Earth is old enough for evolution to have occurred

B) organisms could go extinct

11) 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) a vestigial trait

12) Which of the following, if discovered, could refute our current understanding of the pattern of evolution?
A) no fossils of soft-bodied animals
B) a modern bird having reptile-like scales on its legs
C) radioactive dating of rocks showing that rocks closer to the Earth’s surface are younger than lower rock strata
D) diverse fossils of mammals in Precambrian rock

D) diverse fossils of mammals in Precambrian rock

13) Similar gill pouches in embryos of a chick, human, and cat are an example of _____.
A) structural homology
B) developmental homology
C) genetic homology
D) the inheritance of acquired characters

B) developmental homology

14) The same basic internal organs (kidneys, stomach, heart, lungs) are found in frogs, birds, snakes, and rodents. This is primarily an example of _____.
A) structural homology
B) developmental homology
C) genetic correlation
D) inheritance of acquired characteristics

A) structural homology

15) 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) It must be homologous to some feature in an ancestor.

The figure above contrasts the "Within the artiodactyls" origin of the whale lineage with the "Without the artiodactyls" origin of the whale lineage.

16) One morphological feature of modern cetaceans is a vestigial pelvic girdle. If it is determined that the cetacean lineage diverged from the artiodactyls’ lineage after the divergence of pigs and other artiodactyla, then the vestigial pelvic girdle of cetaceans should be considered a shared _____.
A) ancestral character of the cetartiodactyls
B) derived character of the cetartiodactyls
C) ancestral character of the cetaceans
D) derived character of the cetaceans

D) derived character of the cetaceans

17) Which of the following is the best modern definition of evolution?
A) descent with modification
B) change in the number of genes in a population over time
C) survival of the fittest
D) inheritance of acquired characters

A) descent with modification

18) Given a population that contains genetic variation, what is the correct sequence of the following events under the influence of natural selection?
1. Well-adapted individuals leave more offspring than do poorly adapted individuals.
2. A change occurs in the environment.
3. Genetic frequencies within the population change.
4. Poorly adapted individuals have decreased survivorship.
A) 2 → 4 → 1 → 3
B) 4 → 2 → 1 → 3
C) 4 → 1 → 2 → 3
D) 4 → 2 → 3 → 1
E) 2 → 4 → 3 → 1

A) 2 → 4 → 1 → 3

19) 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) determine if hair length is heritable

20) There is a population of beetles that typically have black wings. A scientist studying these beetles knows that their eggs hatch in early spring, the young insects grow through the late spring and summer, they lay eggs in the early fall, and they die in the early winter. Recently some beetles have been born with white wings. Early in life, the black- and white-winged beetles seem to be very similar in number of mating events, eggs laid, and survival rates, but shortly after laying their eggs the white beetles die and there are only black-winged beetles during the late fall. Which of the following is a true statement about the beetles?
A) White- and black-winged beetles have equal fitness.
B) Black-winged beetles have a higher fitness than white-winged beetles.
C) The number of baby white-winged beetles will decrease in frequency over time.
D) White wings are an adaptation.

A) White- and black-winged beetles have equal fitness.

21) Biological fitness is best defined as
A) A heritable trait that increases the match of an individual to its environment.
B) Variability in the population for a trait that increases survival.
C) Relative the ability of an individual to produce offspring that survive and reproduce.
D) Competition among individuals for resources that allow them to have more offspring.
E) Similar reproductive success among individuals in a population.

C) Relative the ability of an individual to produce offspring that survive and reproduce.

22) 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) Triazine-resistant weeds were more likely to survive and reproduce.

23) 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
E) a mix of both M. tuberculosis strains thrive in the standard cell cultures, but no living bacteria can be found in the cell cultures that contain rifampin

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

24) After the drought of 1977, researchers on the island of Daphne Major hypothesized that medium ground finches that had large, deep beaks, survived better than those with smaller beaks because they could more easily crack and eat the tough Tribulus cistoides fruits. If this hypothesis is correct, what would you expect to observe if a population of these medium ground finches colonizes a nearby island where Tribulus cistoides is the most abundant food for the next 1000 years? Assume that (1) even the survivors of the 1977 drought sometimes had difficulty cracking the tough T. cistoides fruits and would eat other seeds when offered a choice; and (2) food availability is the primary limit on finch fitness on this new island.
A) evolution of yet larger, deeper beaks over time
B) evolution of smaller, pointier beaks over time
C) random fluctuations in beak size and shape
D) no change in beak size and shape

A) evolution of yet larger, deeper beaks over time

25) After the drought of 1977, researchers hypothesized that on the Galápagos island Daphne Major, medium ground finches with large, deep beaks survived better than those with smaller beaks because they could more easily crack and eat the tough Tribulus cistoides fruits. A tourist company sets up reliable feeding stations with a variety of bird seeds (different types and sizes) so that tourists can get a better look at the finches. Which of these events is now most likely to occur to finch beaks on this island?
A) evolution of yet larger, deeper beaks over time, until all birds have relatively large, deep beaks
B) evolution of smaller, pointier beaks over time, until all birds have relatively small, pointy beaks
C) increased variation in beak size and shape over time
D) no change in beak size and shape over time

C) increased variation in beak size and shape over time

The following question is based on information from Frank M. Frey, "Opposing Natural Selection from Herbivores and Pathogens May Maintain Floral-Color Variation in Claytonia virginica (Portulacaceae)," Evolution 58(11), 2004: 2426-37.

26) Claytonia virginica is a woodland spring herb with flowers that vary from white to pale pink to bright pink. Slugs prefer to eat pink-flowering over white-flowering plants (due to chemical differences between the two), and plants experiencing severe herbivory are more likely to die. The bees that pollinate this plant also prefer pink to white flowers, so that Claytonia with pink flowers have greater relative fruit set than Claytonia with white flowers. A researcher observes that the percentage of different flower colors remains stable in the study population from year to year. Given no other information, if the researcher removes all slugs from the study population, what do you expect to happen to the distribution of flower colors in the population over time?
A) The percentage of pink flowers should increase over time.
B) The percentage of white flowers should increase over time.
C) The distribution of flower colors should not change.
D) The distribution of flower colors should randomly fluctuate over time.

A) The percentage of pink flowers should increase over time.

27) The figure above shows the distribution of pocket-mouse coat colors in several Arizona populations found either on light-colored granite substrate or on dark volcanic rock (dark substrate). The Melanocortin-1 receptor (Mc1r) alleles, D and d, differ by four amino acids. Mice with DD and Dd genotypes have dark coats, whereas mice with the dd genotype are light colored. What sort of genotype frequencies might you expect to find in the Xmas, Mid, and O’Neill populations?
A) Xmas-high DD frequency; Mid-high Dd frequency, O’Neill-high dd frequency
B) Xmas-high Dd frequency; Mid-high DD frequency, O’Neill-high dd frequency
C) Xmas-high Dd frequency; Mid-high dd frequency, O’Neill-high DD frequency
D) Xmas-high dd frequency; Mid-high Dd frequency, O’Neill-high DD frequency
E) Xmas-high dd frequency; Mid-high DD frequency, O’Neill-high Dd frequency

E) Xmas-high dd frequency; Mid-high DD frequency, O’Neill-high Dd frequency

28) Refer to the figure above. In their investigation of natural selection on Mc1r alleles (the gene that determines coat color) in Arizona pocket mice, Hoekstra et al. determined the frequency of the D and d alleles in each population. They also determined the frequency of alleles for two neutral mitochondrial DNA genes (genes that do not affect and are not linked to coat color). Why did the researchers include the mitochondrial DNA genes as part of their experimental design?
A) Allele change for the neutral mitochondrial genes serves as an experimental group and gives information on any general background genetic difference among these populations.
B) Allele change for the neutral mitochondrial genes serves as a control and determines coat-color differences among these populations.
C) Allele change for the neutral mitochondrial genes serves as an experimental group and gives information on coat-color differences among these populations.
D) Allele change for the neutral mitochondrial genes serves as a control and gives information on any general background genetic difference among these populations.
E) None of the above answers apply.

D) Allele change for the neutral mitochondrial genes serves as a control and gives information on any general background genetic difference among these populations.

29) 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) Larger doses of DDT should have been applied from the air, into water, and within the soil.
B) All habitats should have received applications of DDT at about the same time.
C) The frequency of DDT application should have been higher.
D) None of the insect pests would have genetic variations that resulted in DDT resistance.
E) DDT application should have been continual.

D) None of the insect pests would have genetic variations that resulted in DDT resistance.

30) 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) These bacteria would be outcompeted and replaced by bacteria that have lost these genes.

31) 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) Each bird’s survival was strongly influenced by the depth and strength of its beak as the drought persisted.

32) 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) the limits of historical constraints

33) 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) Simple morphologies convey some advantage in most parasites.

34) Vestigial traits and neutral changes in DNA sequences are good examples of _____.
A) adaptation
B) acclimation
C) convergent traits
D) nonadaptive traits
E) developmental homology

D) nonadaptive traits

35) Which of the following is a fitness trade-off (compromise)?
A) In some hornbill species, the male helps seal the female in a tree with her nest until the young are ready to fledge.
B) Hummingbirds are the best pollinators of certain flowers, but bees are the best pollinators for orchids.
C) The strong, thick beak of a woodpecker helps it find insects in trees.
D) Turtle shells provide protection but are heavy and burdensome when moving.

D) Turtle shells provide protection but are heavy and burdensome when moving.

36) Over long periods of time, many cave-dwelling organisms have lost their eyes. Tapeworms have lost their digestive systems. Whales have lost their hind limbs. How can natural selection account for these losses?
A) Natural selection cannot account for losses, but accounts only for new structures and functions.
B) Natural selection accounts for these losses by the principle of use and disuse.
C) Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits.
D) The ancestors of these organisms experienced harmful mutations that forced them to lose these structures.

C) Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits.

37) 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 determined by genotype and the environment
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) natural selection is generally limited to modifying structures that were present in previous generations and in previous species

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.

38) The sickle-cell allele is pleiotropic (that is, it affects more than one phenotypic trait). Specifically, this allele affects oxygen delivery to tissues and affects one’s susceptibility to malaria. Under conditions of low atmospheric oxygen availability, individuals heterozygous for this allele can experience life-threatening sickle-cell "crises." Such individuals remain less susceptible to malaria. Thus, pleiotropic genes/alleles reveal that _____.
A) new advantageous alleles do not arise on demand
B) evolution is limited by historical constraints
C) adaptations are often compromises
D) chance events can affect the evolutionary history of populations

C) adaptations are often compromises

1) Evolution in a population of island iguanas can be caused by the following agent(s):
A) Natural selection
B) Genetic drift
C) Gene flow
D) All of the above.
E) Both natural selection and genetic drift.

D) All of the above.

2) 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) = 0.9997, f(A2) = 0.0003
B) f(A1) = 0.9800, f(A2) = 0.0200
C) f(A1) = 0.9700, f(A2) = 0.0300
D) f(A1) = 0.9604, f(A2) = 0.0392
E) f(A1) = 0.9600, f(A2) = 0.0400

C) f(A1) = 0.9700, f(A2) = 0.0300

3) 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) 16%
B) 32%
C) 40%
D) 48%
E) 60%

D) 48%

4) 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
E) random mating

D) no mutation

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

C) no gene flow

6) Refer to the figure above. Is this population in Hardy-Weinberg equilibrium?
A) Yes.
B) No; there are more heterozygotes than expected.
C) No; there are more homozygotes than expected.
D) More information is needed to answer this question.

C) No; there are more homozygotes than expected.

7) A researcher wants to know if gene flow is contributing to evolution of drought tolerance of pitcher plants in a specific bog. As a control, she should
A) Determine if the population is in Hardy-Weinberg equilibrium.
B) Transplant pitcher plants from other populations into the bog.
C) Estimate the frequency of alleles relevant genes for drought tolerance.
D) All of the above.
E) None of these. Gene flow does not contribute to evolution.

A) Determine if the population is in Hardy-Weinberg equilibrium.

8) Why doesn’t inbreeding depression, by itself, cause evolution?
A) It decreases the population’s average fitness.
B) It limits gene flow.
C) It does not change the population’s allele frequencies.
D) It increases homozygosity.
E) It violates the Hardy-Weinberg assumptions.

C) It does not change the population’s allele frequencies.

9) When nonrandom mating occurs in a population so that individuals prefer to mate with similar individuals, allele frequencies should
A) Remain the same, but homozygotes will be overrepresented in the population.
B) Remain the same, but heterozygotes will be overrepresented in the population.
C) Change and heterozygotes will be overrepresented in the population.
D) Change and homozygotes will be overrepresented in the population.
E) Remain the same, at Hardy-Weinberg equilibrium.

A) Remain the same, but homozygotes will be overrepresented in the population.

10) Examine the figure above. What type of selection for body size appears to be occurring in these marine iguanas?
A) directional selection
B) stabilizing selection
C) disruptive selection
D) You cannot determine the type of selection from the above information.

B) stabilizing selection

11) Wikelski and Romero (2003) found that large marine iguanas had higher reproductive success than smaller iguanas did. However, the large iguanas were generally in poor body condition because they could not eat enough; at higher temperatures their foraging efficiency improved, allowing them to eat more. Thus, Wikelski and Romero hypothesized that iguana size will _____ as global warming gradually increases air and water temperatures in the Galápagos Islands.
A) increase
B) decrease
C) stabilize around the mean body size
D) remain unchanged, it is not clear that body size increases fitness

A) increase

12) Currently the only predators of Galápagos marine iguanas are Galápagos hawks. Iguana body size is not correlated with risk of hawk predation, although small iguanas can sprint faster than large iguanas. If predators (for example, cats) that preferably catch and eat slower iguanas are introduced to the island, iguana body size is likely to _____ in the absence of other factors; the iguanas would then be under _____ selection.
A) increase; directional
B) increase; disruptive
C) decrease; directional
D) decrease; disruptive
E) stay the same; stabilizing

C) decrease; directional

13) Three-spined stickleback fish (Gasterosteus aculeatus) show substantial heritable variation in gill-raker length related to differences in their diets. Longer gill rakers appear to function better for capturing open-water prey, while shorter gill rakers function better for capturing shallow-water prey. Which of the following types of selection is most likely to be found in a large lake (open water in the middle and shallow water around the sides) with a high density of these fish?
A) directional selection
B) stabilizing selection
C) disruptive selection
D) sexual selection

C) disruptive selection

14) Cystic fibrosis is a genetic disorder in homozygous recessive (ff) humans that typically causes death in the early thirties. Over time, we would expect the f allele frequency to _____ for this trait.
A) remain the same
B) increase
C) decrease
D) fluctuate

C) decrease

15) Which of the graphs above best represents the relationship between the intensity of directional selection and the genetic variation present within a population?
A) Graph A
B) Graph B
C) Graph C
D) Graph D
E) Graph E

B) Graph B

16) Which of the following statements best summarizes evolution as it is viewed today?
A) Evolution represents the result of selection for acquired characteristics.
B) Evolution is the production of adaptations that meet present and anticipated needs.
C) Evolution is the descent of humans from the present-day great apes.
D) Evolution is the differential survival and reproduction of the most-fit phenotypes.

D) Evolution is the differential survival and reproduction of the most-fit phenotypes.

17) Which of the following is most likely to produce an African butterfly species in the wild whose populations show two strikingly different color patterns?
A) artificial selection
B) directional selection
C) stabilizing selection
D) disruptive selection
E) sexual selection

D) disruptive selection

18) 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) stabilizing selection

19) The recessive allele that causes phenylketonuria (PKU) is harmful, except when an infant’s diet has appropriate levels of the amino acid phenylalanine. What maintains the presence of this harmful allele in a population’s gene pool?
A) heterozygote advantage
B) stabilizing selection
C) diploidy
D) balancing selection

C) diploidy

20) 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) stabilizing selection

21) In seedcracker finches from Cameroon, small- and large-billed birds specialize in cracking soft and hard seeds, respectively. If long-term climatic change resulted in all seeds becoming hard, what type of selection would then operate on the finch population?
A) disruptive selection
B) directional selection
C) stabilizing selection
D) No selection would operate because the population is in Hardy-Weinberg equilibrium.

B) directional selection

22) 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) disruptive selection
C) balancing selection
D) stabilizing selection
E) frequency-dependent selection

E) frequency-dependent selection

23) 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) a genetic bottleneck
B) sexual selection
C) habitat differentiation
D) the founder effect

D) the founder effect

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.)

24) 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) sexual selection
C) gene flow between populations
D) a genetic bottleneck
E) a founder effect

E) a founder effect

25) 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) population bottleneck and Hardy-Weinberg equilibrium
B) heterozygote advantage and stabilizing selection
C) sexual selection and inbreeding depression
D) mutation and natural selection
E) founder effect and genetic drift

E) founder effect and genetic drift

26) In a small population of alpine foxes, you observe increased ear length over a ten-year period. Can you conclude that increase in ear length is advantageous in this population?
A) Yes
B) No

No

27) Genetic drift occurs in a population. Which of the following statements might be true?
A) Genetic drift increased the population’s fitness.
B) Genetic drift decreased the population’s fitness.
C) The population was relatively small.
D) The population experiences a decrease in genetic variation.
E) Any of the statements can be true.

E) Any of the statements can be true.

28) An earthquake decimates a ground-squirrel population, killing 98% of the squirrels. The surviving population happens to have broader stripes, on average, than the initial population. If broadness of stripes is genetically determined, what effect has the ground-squirrel population experienced during the earthquake?
A) directional selection
B) disruptive selection
C) a founder event
D) a genetic bottleneck
E) gene flow

D) a genetic bottleneck

29) Genetic variation _____.
A) is created by the direct action of natural selection
B) arises in response to changes in the environment
C) must be present in a population before natural selection can act upon the population
D) tends to be reduced by when diploid organisms produce gametes

C) must be present in a population before natural selection can act upon the population

30) Which of the following is the most predictable outcome of increased gene flow between two populations?
A) lower average fitness in both populations
B) higher average fitness in both populations
C) increased genetic difference between the two populations
D) decreased genetic difference between the two populations
E) increased genetic drift

D) decreased genetic difference between the two populations

31) Two frog populations (same species) living in two neighboring lakes sing slightly different courtship songs. Increased irrigation makes the land between the two lakes wetter, allowing frogs to expand their ranges to the area between the lakes. Females in both populations prefer loud frogs to quieter frogs, but do not distinguish between the two slightly different songs. Assuming that courtship song differences have a genetic basis, predict what will likely happen to the songs of the two frog populations.
A) The songs will become more similar to each other.
B) Males will become louder.
C) Disruptive selection will cause the songs to differentiate even more.
D) Genetic drift will cause the songs to differentiate even more.
E) You cannot predict a change in the courtship songs at the two lakes.

A) The songs will become more similar to each other.

32) 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) genetic drift

33) 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) Mutations caused major changes in rodent physiology over time.
B) Mutation led to increased genetic variation.
C) Mutation caused genetic drift and decreased fitness.
D) Mutation caused the fixation of new alleles.

B) Mutation led to increased genetic variation.

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

A) does little to change allele frequencies

35) Natural selection _____.
A) is a random process
B) creates beneficial mutations
C) eliminates harmful mutations
D) can favor beneficial mutations

D) can favor beneficial mutations

36) 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, 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 increase in frequency.

C) If the Tamiflu-resistance gene involves a cost, it will experience directional selection leading to reduction in its frequency.

Two populations of birds with somewhat different coloration live on opposite sides of a peninsula. The habitat between the populations is not suitable for these birds. When birds from the two populations are brought together, they produce young whose appearance is intermediate between the two parents. These offspring will breed with each other or with birds from either parent population, and all offspring of these pairings appear intermediate to various degrees.

1) What keeps the two populations separate?
A) temporal reproductive isolation
B) lack of hybrid viability
C) behavioral reproductive isolation
D) habitat isolation

D) habitat isolation

2) The two populations are _____.
A) different subspecies, under the morphological species concept
B) different species, under the biological species concept
C) different species, under the phylogenetic species concept

A) different subspecies, under the morphological species concept

3) Three populations of crickets look very similar, but the males have courtship songs that sound different. What function would this difference in song likely serve if the populations came in contact?
A) a temporal reproductive isolating mechanism
B) a postzygotic isolating mechanism
C) a behavioral reproductive isolating mechanism
D) a gametic reproductive isolating mechanism

C) a behavioral reproductive isolating mechanism

4) Many songbirds breed in North America in the spring and summer and then migrate to Central and South America in the fall. They spend the winter in these warmer areas, where they feed and prepare for the spring migration north and another breeding season. Two hypothetical species of sparrow, A and B, overwinter together in mixed flocks in Costa Rica. In spring, species A goes to the east coast of North America, and species B goes to the west coast. What can you say about the isolating mechanisms of these two species?
A) They must have strong postzygotic isolating mechanisms to spend winter in such close proximity.
B) They must have strong prezygotic isolating mechanisms to spend winter in such close proximity.
C) Their winter habitat has no bearing on their degree of reproductive isolation.
D) Reinforcement must be occurring when they winter together.

C) Their winter habitat has no bearing on their degree of reproductive isolation.

5) Refer to the figure above. Which of the following forms a monophyletic group?
A) A, B, C, D
B) C and D
C) D, E, and F
D) E, F, and G

D) E, F, and G

6) The peppered moth provides a well-known example of natural selection. The light-colored form of the moth was predominant in England before the Industrial Revolution. In the mid-nineteenth century, a dark-colored form appeared. The difference is produced by a dominant allele of one gene. By about 1900, approximately 90% of the moths around industrial areas were dark colored, whereas light-colored moths were still abundant elsewhere. Apparently, birds could readily find the light moths against the soot-darkened background in industrial areas and, therefore, were eating more light moths. Recently, use of cleaner fuels has greatly reduced soot in the landscape, and the dark-colored moths have been disappearing. Should the two forms of moths be considered separate species?
A) Yes, because natural selection has affected the frequency of the two different forms.
B) Yes, because they have completely different coloration.
C) Yes, because they are reproductively isolated based on habitat.
D) Yes, because they have completely different coloration and natural selection has affected the frequency of the two different forms.
E) No.

E) No.

About 3 million years ago, the Isthmus of Panama (a narrow strip of land connecting North and South America) formed, dividing marine organisms into Pacific and Caribbean populations. Researchers have examined species of snapping shrimp on both sides of the isthmus. Based on the morphological species concept, there appeared to be seven pairs of species, with one species of each pair in the Pacific and the other in the Caribbean. The different species pairs live at somewhat different depths in the ocean. Using mitochondrial DNA sequences, the researchers estimated phylogenies and found that each of these species pairs, separated by the isthmus, were indeed each other’s closest relatives. The researchers investigated mating in the lab and found that many species pairs were not very interested in courting with each other, and any that did mate almost never produced fertile offspring. (N. Knowlton, L. A. Weigt, L. A. Solorzano, D. K. Mills, and E. Bermingham. 1993. Divergence in proteins, mitochondrial DNA, and reproductive incompatibility across the Isthmus of Panama. Science 260:1629-32.)

7) Refer to the paragraph about the formation of the Isthmus of Panama. The sister populations on opposite sides of the isthmus are true species under which species concept?
A) the morphological species concept
B) the biological species concept
C) the phylogenetic species concept
D) both the morphological species and phylogenetic species concepts
E) the morpholoogical species, biological species, and phylogenetic species concepts

E) the morpholoogical species, biological species, and phylogenetic species concepts

8) The common edible frog of Europe is a hybrid between two species, Rana lessonae and Rana ridibunda. The hybrids were first described in 1758 and have a wide distribution, from France across central Europe to Russia. Both male and female hybrids exist, but when they mate among themselves, they are rarely successful in producing offspring. What can you infer from this information?
A) Postzygotic isolation exists between the two frog species.
B) Prezygotic isolation exists between the two frog species.
C) These two species are likely in the process of fusing back into one species.
D) The hybrids form a separate species under the biological species concept.

A) Postzygotic isolation exists between the two frog species.

9) Which of the following statements about species, as defined by the biological species concept, is (are) correct?
I. Biological species are defined by reproductive isolation.
II. Biological species are the model used for grouping extinct forms of life.
III. All members of a species can potentially interbreed.
A) I and II
B) I and III
C) II and III
D) I, II, and III

B) I and III

10) Dog breeders maintain the purity of breeds by keeping dogs of different breeds apart when they are fertile. This kind of isolation is most similar to which of the following reproductive isolating mechanisms?
A) temporal isolation
B) behavioral isolation
C) mechanical isolation
D) habitat isolation
E) gametic isolation

D) habitat isolation

11) Rank the following in order from most general to most specific:
1. gametic isolation
2. reproductive isolating mechanism
3. sperm-egg incompatibility in sea urchins
4. prezygotic isolating mechanism
A) 2, 3, 1, 4
B) 2, 4, 1, 3
C) 4, 1, 2, 3
D) 4, 2, 1, 3
E) 2, 1, 4, 3

B) 2, 4, 1, 3

12) Rocky Mountain juniper (Juniperus scopulorum) and one-seeded juniper (J. monosperma) have overlapping ranges. Pollen grains (which contain sperm cells) from one species are unable to germinate and make pollen tubes on female ovules (which contain egg cells) of the other species. These two juniper species are kept separate by _____.
A) habitat isolation
B) temporal isolation
C) gametic isolation
D) behavioral isolation
E) isolation

C) gametic isolation

13) What does the biological species concept use as the primary criterion for determining species boundaries?
A) geographic isolation
B) niche differences
C) gene flow
D) morphological similarity
E) molecular (DNA, RNA, protein) similarity

C) gene flow

On the volcanic, equatorial West African island of Sao Tomé, two species of fruit fly exist. Drosophila yakuba inhabits the island’s lowlands, and is also found on the African mainland, located about two hundred miles away. At higher elevations, and only on Sao Tomé, is found the very closely related Drosophila santomea. The two species can hybridize, though male hybrids are sterile. A hybrid zone exists at middle elevations, though hybrids there are greatly outnumbered by D. santomea. Studies of the two species’ nuclear genomes reveal that D. yakuba on the island is more closely related to mainland D. yakuba than to D. santomea (2n = 4 in both species). Sao Tomé rose from the Atlantic Ocean about fourteen million years ago.

14) Which of the following reduces gene flow between the gene pools of the two species on Sao Tomé, despite the existence of hybrids?
A) gametic isolation
B) reduced hybrid viability
C) hybrid sterility
D) temporal isolation
E) a geographic barrier

C) hybrid sterility

15) The observation that island D. yakuba are more closely related to mainland D. yakuba than island D. yakuba are to D. santomea is best explained by proposing that D. santomea _____.
A) descended from a now-extinct, non-African fruit fly
B) arrived on the island before D. yakuba
C) descended from a single colony of D. yakuba, which had been introduced from elsewhere, with no subsequent colonization events
D) descended from an original colony of D. yakuba, of which there are no surviving members. The current island D. yakuba represent a second colonization event from elsewhere

D) descended from an original colony of D. yakuba, of which there are no surviving members. The current island D. yakuba represent a second colonization event from elsewhere.

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.

16) Which type of reproductive isolation operates to keep the mosquitofish isolated, even when fish from different ponds are reunited in the same body of water?
A) behavioral isolation
B) habitat isolation
C) temporal isolation
D) mechanical isolation
E) gametic isolation

A) behavioral isolation

17) There are currently two large, permanent bridges that span the Panama Canal. The bridges are about eight miles apart. If snapping shrimp avoid swimming at night and avoid swimming under shadows, then what do these bridges represent for the snapping shrimp?
A) sources of refuge
B) geographic barriers
C) sources of a hybrid zone between the two bridges
D) sources for increased gene flow

B) geographic barriers

18) The largest unit within which gene flow can readily occur is _____.
A) a population
B) a species
C) the entire range of a genus
D) the hybrid zone
E) the entire range of a phylum

B) a species

19) Males of different species of the fruit fly Drosophila that live in the same parts of the Hawaiian Islands have different elaborate courtship rituals. These rituals involve fighting other males and making stylized movements that attract females. What type of reproductive isolation does this represent?
A) habitat isolation
B) temporal isolation
C) behavioral isolation
D) gametic isolation

C) behavioral isolation

20) Bird guides once listed the myrtle warbler and Audubon’s warbler as distinct species. Recently, these birds have been classified as eastern and western forms of a single species, the yellow-rumped warbler. Which of the following pieces of evidence, if true, would be cause for this reclassification?
A) The two forms interbreed often in nature, and their offspring have good survival and reproduction.
B) The two forms live in similar habitats.
C) The two forms have many genes in common.
D) The two forms have similar food requirements.
E) The two forms are very similar in coloration.

A) The two forms interbreed often in nature, and their offspring have good survival and reproduction.

About 3 million years ago, the Isthmus of Panama (a narrow strip of land connecting North and South America) formed, dividing marine organisms into Pacific and Caribbean populations. Researchers have examined species of snapping shrimp on both sides of the isthmus. Based on the morphological species concept, there appeared to be seven pairs of species, with one species of each pair in the Pacific and the other in the Caribbean. The different species pairs live at somewhat different depths in the ocean. Using mitochondrial DNA sequences, the researchers estimated phylogenies and found that each of these species pairs, separated by the isthmus, were indeed each other’s closest relatives. The researchers investigated mating in the lab and found that many species pairs were not very interested in courting with each other, and any that did mate almost never produced fertile offspring. (N. Knowlton, L. A. Weigt, L. A. Solorzano, D. K. Mills, and E. Bermingham. 1993. Divergence in proteins, mitochondrial DNA, and reproductive incompatibility across the Isthmus of Panama. Science 260:1629-32.)

21) Refer to the paragraph about the formation of the Isthmus of Panama. If the isthmus formed gradually rather than suddenly, what pattern of genetic divergence would you expect to find in these species pairs?
A) similar percentages of difference in DNA sequence between all pairs of sister species
B) greater percentage of difference in DNA sequence between species that inhabit deep water than between species that inhabit shallow water
C) greater percentage of difference in DNA sequence between species that inhabit shallow water than between species that inhabit deep water

B) greater percentage of difference in DNA sequence between species that inhabit deep water than between species that inhabit shallow water

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.

22) Which two of the following have operated to increase divergence between mosquitofish populations on Andros?
1. improved gene flow
2. bottleneck effect
3. sexual selection
4. founder effect
5. natural selection
A) 1 and 3
B) 2 and 3
C) 2 and 4
D) 3 and 4
E) 3 and 5

E) 3 and 5

23) Why should deepwater shrimp on different sides of the isthmus have diverged from each other earlier than shallow-water shrimp?
A) They have been geographically isolated from each other for a longer time.
B) Cold temperatures, associated with deep water, have accelerated the mutation rate, resulting in faster divergence in deepwater shrimp.
C) The rise of the land bridge was accompanied by much volcanic activity. Volcanic ash contains heavy metals, which are known mutagens. Ash fall caused high levels of heavy metals in the ocean sediments underlying the deep water, resulting in accelerated mutation rates and faster divergence in deepwater shrimp.
D) Fresh water entering the ocean from the canal is both less dense and cloudier than seawater. The cloudy fresh water interferes with the ability of shallow-water shrimp to locate mating partners, which reduces the frequency of mating, thereby slowing the introduction of genetic variation.

A) They have been geographically isolated from each other for a longer time.

24) In which habitat should one find snapping shrimp most closely related to shrimp that live in habitat A4?
A) A3
B) A5
C) B4
D) either A3 or A5
E) any species from any one of the side A habitats

C) B4

25) Which of these habitats is likely to harbor the most recently diverged species?
A) A5
B) B4
C) A3
D) B2
E) A1

E) A1

26) Which habitats should harbor snapping shrimp species with the greatest degree of genetic divergence from each other?
A) A1 and A5
B) A1 and B5
C) B5 and B1
D) A5 and B5
E) Both A1/A5 and B1/B5 should have the greatest, but equal amounts of, genetic divergence.

D) A5 and B5

27) Which factor is most important for explaining why there are equal numbers of snapping shrimp species on either side of the isthmus?
A) the relative shortness of time they have been separated
B) the depth of the ocean
C) the number of actual depth habitats between the surface and the sea floor
D) the elevation of the isthmus above sea level
E) the depth of the canal

A) the relative shortness of time they have been separated

28) The Panama Canal was completed in 1914, and its depth is about fifty feet. After 1914, snapping shrimp species from which habitats should be most likely to form hybrids as the result of the canal?
A) A5 and B5
B) A3 and B3
C) A1 and B1
D) either A1 and A2, or B1 and B2
E) A1-A3 and B1-B3 have equal likelihoods of harboring snapping shrimp species that can hybridize.

C) A1 and B1

29) Which of the following describes the most likely order of events in allopatric speciation?
A) genetic drift, genetic isolation, divergence
B) genetic isolation, divergence, genetic drift
C) divergence, genetic drift, genetic isolation
D) divergence, genetic isolation, genetic drift
E) genetic isolation, genetic drift, divergence

E) genetic isolation, genetic drift, divergence

30) There is an island in the middle of a large river that houses a large population of ants. Damming of the river causes the island to flood and only the highest points of the island are now above water. The ants cannot swim, so are now in multiple isolated populations. Which of the following best describes this event?
A) This situation represents isolation by dispersal.
B) This situation represents isolation by vicariance.
C) This situation represents a form of sympatric speciation.
D) Only a rare development of polyploidy could lead to speciation in this case.
E) Speciation will not occur in this case because of gene flow.

B) This situation represents isolation by vicariance.

31) How are two different species most likely to evolve from one ancestral species?
A) sympatrically, by a point mutation affecting morphology or behavior
B) sympatrically, due to extensive inbreeding
C) allopatrically, due to extensive inbreeding
D) allopatrically, after the ancestral species has split into two populations

D) allopatrically, after the ancestral species has split into two populations

32) Which of the following could be a vicariance event for species in that habitat?
A) The level of water in a lake recedes, creating two lakes where there used to be one.
B) Some insects get blown in a storm to a new mountain range, where they lay eggs.
C) Radiation near Chernobyl increases mutation rates, causing an increase in autopolyploidy.
D) Global warming allows populations of mosquitoes to survive at higher elevations.

A) The level of water in a lake recedes, creating two lakes where there used to be one

33) Which of the following does not tend to promote speciation?
A) the founder effect
B) gene flow
C) natural selection
D) polyploidy
E) disruptive selection

B) gene flow

34) House finches were found only in western North America until 1939, when a few individuals were released in New York City. These individuals established a breeding population and gradually expanded their range. The western population also expanded its range somewhat eastward, and the two populations have recently come in contact. If the two forms were unable to interbreed when their expanding ranges met, it would be an example of _____.
A) prezygotic isolation
B) reinforcement
C) autopolyploidy
D) allopatric speciation
E) sympatric speciation

D) allopatric speciation

35) Most causes of speciation are relatively slow, in that they may take many generations to see changes, with the exception of _____.
A) polyploidy
B) reinforcement
C) colonization
D) natural selection

A) polyploidy

36) Two researchers experimentally formed tetraploid frogs by fertilizing diploid eggs from Rana porosa brevipoda with diploid sperm from Rana nigromaculata. When they mated these tetraploid frogs with each other, most of the offspring that survived to maturity were tetraploid, with chromosome sets of both diploid parent species. Based on these results, if this type of tetraploid formed in the wild, what would be the result? (Y. Kondo and A. Kashiwagi. 2004. Experimentally induced autotetraploidy and allotetraploidy in two Japanese pond frogs. Journal of Herpetology 38(3):381-92.)
A) The two parent species would interbreed and fuse into one species.
B) The two parent species would recognize each other as mates.
C) The tetraploids would be reproductively isolated from both parent species.
D) The tetraploids would be selected against.

C) The tetraploids would be reproductively isolated from both parent species.

37) Why is speciation by polyploidy more likely in plants than in animals?
A) Plant gametes can be produced by meiosis from somatic cells that have undergone many rounds of mitosis.
B) Plant gametes lack postzygotic isolating mechanisms.
C) Plants are sessile and, therefore, are never prezygotically isolated to ensure reproduction.
D) Plants are sessile and cannot speciate via dispersal.
E) Plants lack the DNA repair enzymes that animals have.

A) Plant gametes can be produced by meiosis from somatic cells that have undergone many rounds of mitosis.

38) Which of the following statements explains why animals are less likely than plants to speciate by polyploidy?
A) Animals self-fertilize less often than plants, so diploid gametes are less likely to fuse.
B) Animals have better mechanisms for repairing chromosomes than plants have.
C) Animals are more mobile, so they have more effective prezygotic isolating mechanisms.
D) Animals are more mobile, so populations get separated far less often.
E) Animals use a more rigorous form of meiosis than plants, making diploid gametes much more difficult to form.

A) Animals self-fertilize less often than plants, so diploid gametes are less likely to fuse.

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