BIO 1 Chapter 24

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. What is the best way to promote fusion between two related populations of mosquitofish, one of which lives in a predator-rich pond and the other of which lives in a predator-poor pond? A) Build a canal linking the two ponds that permits free movement of mosquitofish, but not of predators. B) Transfer only female mosquitofish from a predator-rich pond to a predator-poor pond. C) Perform a reciprocal transfer of females between predator-rich and predator-poor ponds. D) Remove predators from a predator-rich pond and transfer them to a predator-poor pond.

(A) Build a canal linking the two ponds that permits free movement of mosquitofish, but not of predators.

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.

Two species of tree frogs that live sympatrically in the northeastern United States differ in ploidy: Hyla chrysoscelis is diploid, and Hyla versicolor is tetraploid. The frogs are identical in appearance, but their mating calls, which females use to find mates, differ. Which likely evolved first? A) Polyploidy B) Reproductive isolation C) Behavioral isolation D) All of the above evolved at the same time.

(A) Polyploidy

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 the hybrids mate with other hybrids or with adults of either species, 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.

Which of the following could be a vicariance event? 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.

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.

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.

Which process led to the formation of the species pairs of Pacific and Caribbean snapping shrimp? A) allopatric speciation by vicariance B) allopatric speciation by dispersal C) sympatric speciation by vicariance D) sympatric speciation by dispersal

(A) allopatric speciation by vicariance

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. 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

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. 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 D) none of the above.

(A) different subspecies, under the morphological species concept

A researcher notices that in a certain moth species, some females prefer to feed and lay eggs on domesticated solanaceous plants like potatoes and tomatoes. Other females prefer to feed and lay eggs on wild solanaceous plants like Datura. Both male and female moths primarily use scent to find these plants from afar. Females tend to mate where they feed, and the researcher finds a genetic basis for scent preference in these moths. Based on the above information, what might be occurring in this moth species? A) divergence in sympatry B) divergence due to habitat fragmentation C) postzygotic isolation D) polyploidization

(A) divergence in sympatry

In hybrid zones where reinforcement is occurring, you should see a decline in ________. A) gene flow between distinct gene pools B) speciation C) the genetic distinctness of two gene pools D) mutation rates E) hybrid sterility

(A) gene flow between distinct gene pools

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

In a hypothetical situation, a certain species of flea feeds only on pronghorn antelopes. In the western United States, pronghorns and cattle often associate with one another in the same open rangeland. Some of these fleas develop a strong preference for cattle blood and mate only with other fleas that prefer cattle blood. The host mammal can be considered as the fleas' habitat. If this situation persists, and new species evolve, this would be an example of ________. A) sympatric speciation and habitat isolation B) sympatric speciation and temporal isolation C) allopatric speciation and habitat isolation D) allopatric speciation and gametic isolation

(A) sympatric speciation and habitat isolation

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

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

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.

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

A hybrid zone is properly defined as ________. A) an area where the ranges of two closely related species overlap, but do not interbreed B) an area where mating occurs between members of two closely related species, producing viable offspring C) a zone where sterile hybrids form, kept separate by postzygotic barriers D) an area where members of two closely related species intermingle, but gene flow is prevented by prezygotic barriers

(B) an area where mating occurs between members of two closely related species, producing viable offspring

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

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

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

Reinforcement is most likely to occur when ________. A) the environment is changing B) hybrids have lower fitness than either parent population C) prezygotic isolating mechanisms are in place D) gene flow is low

(B) hybrids have lower fitness than either parent population

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 200 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, but 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 14 million years ago. If the low number of hybrid flies in the hybrid zone, relative to the number of D. santomea flies there, is due to the fact that hybrids are poorly adapted to conditions in the hybrid zone, and if fewer hybrid flies are produced with the passage of time, these conditions will most likely lead to ________. A) fusion B) reinforcement C) stability D) further speciation events

(B) reinforcement

The origin of a new plant species by hybridizing two existing species, coupled with accidents during cell division, is an example of ________. A) allopatric speciation and autopolyploidy B) sympatric speciation and allopolyploidy C) allopatric speciation and allopolyploidy D) sympatric speciation and autopolyploidy

(B) sympatric speciation and allopolyploidy

Beetle pollinators of a particular plant are attracted to its flowers' bright orange color. The beetles not only pollinate the flowers but mate while inside of the flowers. A mutant version of the plant with red flowers becomes more common with the passage of time. A particular variant of the beetle prefers the red flowers to the orange flowers. Over time, these two beetle variants diverge from each other to such an extent that interbreeding is no longer possible. What kind of speciation has occurred in this example, and what has driven it? A) allopatric speciation; temporal isolation B) sympatric speciation; habitat isolation C) allopatric speciation; behavioral isolation D) sympatric speciation; sexual selection E) sympatric speciation; allopolyploidy

(B) sympatric speciation; habitat isolation

The Panama Canal was completed in 1914, and its depth is about 50 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

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

Male frogs give calls that attract female frogs to approach and mate. Researchers examined mating calls of closely related tree frogs in South America. If reinforcement is occurring, what would you expect if you compare the calls of the two species in zones of sympatry versus zones of allopatry? A) Calls would be equally similar in both areas. B) Calls would be more similar in areas of sympatry. C) Calls would be more different in areas of sympatry. D) None of the above outcomes would be expected.

(C) Calls would be more different in areas of sympatry.

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.

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.

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

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

Rocky Mountain juniper (Juniperus scopulorum) and one-seeded juniper (J. monosperma) have overlapping ranges. Pollen grains (which contain sperm nuclei) from one species are unable to germinate and make pollen tubes to bring the sperm nuclei to the 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) morphological isolation

(C) gametic isolation

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 200 miles away. The very closely related species Drosophila santomea is found at higher elevations and only on Sao Tomé. The two species can hybridize, though male hybrids are sterile. A hybrid zone exists at middle elevations, where hybrids 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 14 million years ago. 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

A small number of birds arrive on an island from a neighboring larger island. This small population begins to adapt to the new food plants available on the island as selection favors those birds with larger beaks. About twice a year, one or two more birds from the neighboring island arrive. These new arrivals ________. A) speed up the process of speciation B) tend to promote adaptation to the new food plants C) tend to retard adaptation to the new food plants D) represent a colonizing event

(C) tend to retard adaptation to the new food plants

Plant species A has a diploid number of 12. Plant species B has a diploid number of 16. A new species, C, arises as an allopolyploid from A and B. The diploid number for species C would probably be ________. A) 12 B) 14 C) 16 D) 28 E) 56

(D) 28

Refer to the accompanying figure. 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

Male frogs give calls that attract female frogs to approach and mate. Researchers examined mating calls of closely related but separate species of tree frogs in South America. What outcomes could possibly occur where the ranges of two species overlap? I. The species will interbreed, eventually fusing over time. II. A stable hybrid zone will form if hybrids are better adapted to the area of overlap than either parent species is. III. Species will continue to diverge and be isolated by behavioral or genetic mechanisms. A) I B) II C) III D) I, II, and III

(D) I, II, and III

A female fly, full of fertilized eggs, is swept by high winds to an island far out to sea. She is the first fly to arrive on this island and the only fly to arrive in this way. Thousands of years later, her numerous offspring occupy the island, but none of them resembles her. There are, instead, several species, each of which eats only a certain type of food. None of the species can fly and their balancing organs (halteres) are now used in courtship displays. The male members of each species bear modified halteres that are unique in appearance to their species. Females bear vestigial halteres. The ranges of all of the daughter species overlap. Fly species W, found in a certain part of the island, produces fertile offspring with species Y. Species W does not produce fertile offspring with species X or Z. If no other species can hybridize, then which of the following statements about species W and Y is/are TRUE? I. Species W and Y have genomes that are still similar enough for successful meiosis to occur in hybrid flies. II. Species W and Y have more genetic similarity with each other than either did with the other two species. III. Species W and Y may fuse into a single species if their hybrids remain fertile over the course of many generations. A) Only I is correct. B) Only II is correct. C) Only III is correct. D) I, II, and III are correct.

(D) I, II, and III are correct.

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

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

The phenomenon of fusion is likely to occur when, after a period of geographic isolation, two populations meet again and ________. A) their chromosomes are no longer homologous enough to permit meiosis B) an increasing number of infertile hybrids is produced over the course of the next 100 generations C) no reproduction occurs in the hybrid zone D) an increasing number of viable, fertile hybrids is produced over the course of the next 100 generations E) a decreasing number of viable, fertile hybrids is produced over the course of the next 100 generations

(D) an increasing number of viable, fertile hybrids is produced over the course of the next 100 generations

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 200 miles away. The very closely related species Drosophila santomea is found at higher elevations and only on Sao Tomé. The two species can hybridize, though male hybrids are sterile. A hybrid zone exists at middle elevations, where hybrids 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 14 million years ago. 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

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

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. 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

Among known plant species, which of these have been the two most commonly occurring phenomena that have led to the origin of new species? A) allopatric speciation and sexual selection B) allopatric speciation and polyploidy C) sympatric speciation and sexual selection D) sympatric speciation and polyploidy

(D) sympatric speciation and polyploidy

The data collected by the researchers indicate that ________. A) a hybrid zone was established after the completion of the bridge B) there was no migration between the two squirrel populations after the bridge was completed C) gene flow occurred from one type of squirrel into the gene pool of the other type of squirrel D) two-way migration of squirrels occurred across the bridge but without hybridization E) some northern squirrels migrated south, but no southern squirrels migrated north across the bridge

(D) two-way migration of squirrels occurred across the bridge but without hybridization

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

Which of these habitats is likely to harbor the most recently diverged species? A) A5 and B5 B) A4 and B4 C) A3 and B3 D) A2 and B2 E) A1 and B1

(E) A1 and B1

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. The dark- and light-colored forms readily interbreed with each other. By about 1900, approximately 90 percent 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.

Suppose that a group of male pied flycatchers migrated from a region where there were no collared flycatchers to a region where both species were present. Assuming events like this are very rare, which of the following scenarios is LEAST likely? A) The frequency of hybrid offspring would increase. B) Migrant pied males would produce fewer offspring than would resident pied males. C) Pied females would rarely mate with collared males. D) Migrant males would mate with collared females more often than with pied females. E) The frequency of hybrid offspring would decrease.

(E) The frequency of hybrid offspring would decrease.

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

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.) 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 morphological species, biological species, and phylogenetic species concepts

(E) the morphological species, biological species, and phylogenetic species concepts

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.