Chapter 24

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

polyploidy

The most likely explanation for the high rate of sympatric speciation that apparently existed among the cichlids of Lake Victoria in the past is

sexual selection.

which of the following outcomes is most likely in hybrid zones where reinforcement of isolating mechanisms is occurring

speciation

which of the following statements most accurately applies to speciation

speciation can involve a change to a single gene

According to the concept of punctuated equilibrium, the "sudden" appearance of a new species in the fossil record means that

speciation occurred rapidly in geologic time

The largest unit within which gene flow can readily occur is a

species

which of the following characteristics is a postzygotic barrier that prevents hybrids between two species from producing offspring

hybrid breakdown

Among known plant species, which of these have been the two most commonly occurring phenomena that have led to the origin of new species? 1. allopatric speciation 2. sympatric speciation 3. sexual selection 4. polyploidy

2 and 4

what is both a morphological and phylogenetic species concept (2)

- accomodates asexual reproduction - species acceptance criteria can be subjective

Gametes from two plant species combine and produce a haploid zygote, and that zygote develops into a haploid, hybrid plant. Why is the hybrid plant sterile? (2)

- meiosis cannot occur - the cells do not contain homologous chromosomes

Calculate the value of the reproductive isolation index if salamanders were equally successful in mating with members of their own population and members of another population.

Rocky Mountain juniper (Juniperus scopulorum) and one-seeded juniper (J. monosperma) have overlapping ranges. If 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, then which of these terms are applicable? 1. sympatric species 2. prezygotic isolation 3. postzygotic isolation 4. allopatric species 5. habitat isolation 6. reduced hybrid fertility

1 and 2

The question refers to the following description. 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, 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 14 million years ago. If a speciation event occurred on Sao Tomé, producing D. santomea from a parent colony of D. yakuba, then which terms apply? I. macroevolution II allopatric speciation III. sympatric speciation

1 and 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. The biological species is the largest unit of population in which successful interbreeding is possible.

1 and 3

In a hypothetical situation, a certain species of flea feeds only on pronghorn antelopes. In rangelands of the western United States, pronghorns and cattle often associate with one another. If some of these fleas develop a strong preference for cattle blood and mate only with other fleas that prefer cattle blood, then over time which of these should occur, if the host mammal can be considered as the fleas' habitat? 1. reproductive isolation 2. sympatric speciation 3. habitat isolation 4. prezygotic barriers

1 through 4

The question refers to the following description. 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. The predatory fish rely on visual cues and speed to capture mosquitofish. Mosquitofish rely on speed and visual cues to avoid the predatory fish. Which adaptation(s) might help the predators survive in ponds that are home to faster mosquitofish? 1. directional selection for increased speed 2. stabilizing selection for speed that matches that of the mosquitofish 3. change in hunting behavior that replaces reliance on visual cues with reliance on tactile cues, which can be used to hunt at night 4. change in hunting behavior that eliminates speed in favor of better camouflage, which permits an ambush strategy

1, 3, or 4

which of the following statements is the best definition of a hybrid zone

an area where matung occurs between members of two closely related species, producing viable offspring

Rank the following from most general to most specific: 1. gametic isolation 2. reproductive isolating mechanism 3. sperm-egg incompatibility in sea urchins 4. prezygotic isolating mechanism

2,4,1,3

Calculate the value of the reproductive isolation index if all of the matings within a population were successful but none of the matings between populations were successful.

2.0

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

3,4

Of the 59 matings in the experimental groups, how many were between like-adapted flies (flies adapted to the same medium)?

What is genetic drift?

A change in allele frequencies caused by random events

gametic isolation

A prezygotic reproductive barrier where the sperm of one species may not be able to fertilize the eggs of another species

There are two groups of pine trees that appear to be very similar phenotypically and genotypically. However, one releases pollen in January, when the female structures of that group are receptive, and one in March. What kind of reproductive barrier is this? A)Temporal isolation B)Hybrid inviability C)Gametic isolation D)Mechanical isolation E)A geographic barrier

A)Temporal isolation

Sympatric speciation typically occurs by all of the following mechanisms except __________. A)a geographic barrier splitting a population B)polyploidy C)habitat differentiation D)autopolyploidy E)allopolyploidy F)sexual selection

A)a geographic barrier splitting a population

in a species that has two chromosomes, suppose that a male has genotype aa for a gene on chromosome 1 and genotype bb for a gene on chromosome 2. If a female of this species has genotype AA for the gene on chromosome 1 and genotype BB for the gene on chromosome 2, which of the following represents the possible genotypes in a cell of their offspring

Aa on chromosome 1, Bb on chromosome 2

Feathers either play a role, or may have played a role, in _____.

All of these (extended hops, courtship, flight, and gliding).

Why are the large finches now living on the Galápagos Islands different from the original source population from a nearby island? A)All three answers are correct. B)Genetic drift occurred in the two populations. C)Natural selection favored individuals that were more fit in the new environment. D)The separation of habitats reduced gene flow between the populations.

All three answers are correct.

In order for speciation to occur, what must be true?

At least one gene, affecting at least one phenotypic trait, must change.

Imagine that part of a population of South American finches is blown by a storm onto an island far offshore and manages to survive and reproduce there for a period of 10,000 years. After that period, a climate change results in lower sea levels and the reconnection of the island with the mainland. Members of the formerly isolated island finch population can now interact freely with members of the original mainland population. Which of the following observations would, by itself, lead you to conclude unequivocally that the island finch population had evolved into a distinct species, according to the biological species concept? A)The island birds all have red feathers, but the mainland birds have green feathers. B)Individuals from the different populations sometimes mate with each other, but all of the resulting eggs are sterile. C)Individuals from the different populations frequently direct courtship behavior toward members of the other population. D)Hybrid offspring of matings between individuals from the two populations do not look like either parent. E)The preferred food of the island birds is quite different from the diet of mainland birds.

B)Individuals from the different populations sometimes mate with each other, but all of the resulting eggs are sterile.

In which of the following groups has sympatric speciation been most important? A)Fungi B)Bacteria C)Plants D)Protozoa E)Animals

C)Plants

The original habitat of the North American maggot fly, Rhagoletis pomonella, was native hawthorn trees. About 200 years ago, some populations colonized newly introduced apple trees. The two populations are still classified as subspecies, but sympatric speciation is under way. What has contributed to incipient speciation in the maggot fly?

Because apples mature more quickly than hawthorn fruit, the apple-feeding flies have been selected for more rapid development. This has led to temporal isolation between hawthorn and apple maggot flies. Read about Rhagoletis pomonella speciation.

Three of the most prominent definitions of species are the biological species concept, the phylogenetic species concept, and the morphological species (morphospecies) concept. Drag each characteristic to the appropriate bin based on the species concept(s) to which it applies.

Biological: Not applicable for extinct species Morphological: Relies on similarities in structure Phylogenetic: Based on evolutionary history Morphological and Phylogenetic: Accommodates asexual reproduction Species acceptance criteria can be subjective Morphological, Phylogenetic, and Biological: Used by scientists in classification

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

According to the punctuated equilibrium model of evolution, __________. A)isolated species changing over a few thousand generations represent graduated equilibrium, not punctuated equilibrium B)None of the listed responses is correct. C)fossils of organisms that existed during periods of stasis should be as abundant as those of organisms that existed during periods of rapid change D)the tempo of evolution consists of abrupt episodes of speciation among long periods of equilibrium E)polyploidy is not a mechanism of punctuated equilibrium

D)the tempo of evolution consists of abrupt episodes of speciation among long periods of equilibrium

true or false: the last ice age produced many different species mainly because populations dispersed and colonized new habitats

False

Which of the following statements is supported by the data from the control group matings?

Flies were about as likely to mate with flies from different starch-adapted populations as with flies from their own starch-adapted population.

What is true of the flightless cormorants of the Galápagos Islands?

Flightless cormorants on one island have restricted gene flow with those on other islands, which could someday lead to a macroevolutionary event.

Which of the following factors would not contribute to allopatric speciation?

Gene flow between the two populations is extensive.

Which hypothesis suggests a possible cause of the relationship shown in the scatter plot?

Geographically separated populations of dusky salamanders gradually diverge, and the divergence increases with geographic distance.

In Europe, there is a long narrow hybrid zone, shown in red on the map, between the high-altitude habitat of the yellow-bellied toad and the lowland habitat of the fire-bellied toad. Despite this, there is little gene flow between the two species. Select the correct explanation. A)Yellow-bellied toads and fire-bellied toads are two different species. B)Hybrids have poor survival and reproduction and thus produce few viable offspring with members of either parent species. C)Toads mate only with their own kind in order to avoid producing unhealthy hybrid young.

Hybrids have poor survival and reproduction and thus produce few viable offspring with members of either parent species.

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. I II III I, II, and III

I, II, and III

A population of birds colonizes an area in which the insects upon which they feed live inside trees. Which of the following events accounts for an observed increase in average beak size in the bird population over time?

Increased fitness of large-beaked birds, leading to natural selection

what role does nondisjunction play in the formation of a fertile allopolyploid hybrid

It doubles the chromosome number in the hybrid.

What is true of macroevolution?

It is evolution above the species level.

Select the correct statement describing sympatric speciation.

Sympatric speciation can occur in a single generation. Read about autopolyploidy and sympatric speciation.

How can an allopolyploid plant become a biologically fit new species?

Nondisjunction event during mitosis

which of these is an example of temporal isolation

One species is nocturnal, and the other species is not.

Adaptive radiations on archipelagos (island chains) represent some of the best-understood speciation events. Why is an ancestral species more likely to give rise to multiple descendent species on an archipelago than on an equal-sized area of mainland? A)Favorable mutations are more likely to arise on an archipelago as populations try to adapt to conditions on their specific island. B)By chance, different species will colonize different islands in a chain. C)Populations on nearby islands are more likely to be genetically isolated than populations that are equally close to one another on the mainland.

Populations on nearby islands are more likely to be genetically isolated than populations that are equally close to one another on the mainland.

Populations on nearby islands are more likely to be genetically isolated than populations that are equally close to one another on the mainland. Regions that are highly subdivided by geographic barriers such as archipelagos typically have more species than do regions with fewer barriers. The barriers lead to reproductive isolation between populations, initiating allopatric speciation.

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)These two species are likely in the process of fusing back into one species. B)Postzygotic isolation exists between the two frog species. C)The hybrids form a separate species under the biological species concept. D)Prezygotic isolation exists between the two frog species.

Postzygotic isolation exists between the two frog species.

which of the following statements about reinforcement is true

Reinforcement is a type of natural selection

Which of the following statements about reinforcement is true? A)Reinforcement is also called dispersive selection. B)Reinforcement increases the number of intermediate phenotypes. C)Reinforcement decreases the morphological difference between two incipient species. D)Reinforcement is a type of natural selection.

Reinforcement is a type of natural selection.

What hypothesis did the researchers test in this study?

Reproductive isolation increases with geographic distance between dusky salamander populations.

What does the scatter plot suggest about the process of allopatric speciation?

Reproductive isolation is more likely to occur as populations become separated by greater distances.

Review the scatter plot (Figure 1) of reproductive isolation value versus geographic distance for 27 pairs of dusky salamander populations. (Select Figure 2 from the drop-down menu above the data table.) How do reproductive isolation values change with geographic distance among pairs of dusky salamander populations?

Reproductive isolation values increase with geographic distance.

Which of the following statements about speciation is correct?

Speciation is a basis for understanding macroevolution.

Recall that the biological species concept defines a species as a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring. This means that all members of these populations (called conspecifics) can contribute to a common gene pool. Conspecifics are organisms or populations that belong to the same species. Genes are transferred between conspecific populations through both direct and indirect gene flow. Biologists studying disease susceptibility in mice used genetic techniques to look for gene flow in 12 wild populations of mice. The populations (designated A through L) were located along a 210-km transect line.The researchers found evidence of gene flow between some, but not all, pairs of populations. In the grid below, a "+" indicates a pair of populations in which direct gene flow was detected, and a "-" indicates a pair that showed no evidence of direct gene flow. For help reading this grid, see Hint 2.The researchers discovered that the 12 populations could be organized into 3 distinct species. Populations A, B, and C each belong to a different species. Use the data in the grid to sort each population to the species to which it belongs.

Species 1 (includes population A): D F H I K Species 2 (includes population B): L E Species 3 (includes population C): G J

which of the following statements best describes macroevolution

macroevolution is evolution above the species level

A narrow hybrid zone separates the toad species Bombina bombina and Bombina variegata. What is true of those alleles that are unique to the parental species?

The alleles' heterozygosity should be higher among the hybrid toads there.

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 (see Figure 24.15 in your textbook). Assuming events like this are very rare, which of the following scenarios is least likely?

The frequency of hybrid offspring would decrease.

A subset of a population of birds leaves its habitat on the mainland and colonizes a nearby island. The birds, after a period of time, become reproductively isolated. The island sinks and the population of birds that lived on the island returns to itsoriginal habitat. Which of the following statements about these bird populations is true?

The populations will not be able to interbreed because they are different species.

Which of the following statements is best supported by the data on matings in the experimental groups?

The starch-adapted flies and maltose-adapted flies are not different species, but a reproductive barrier is forming between the populations.

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 tetraploids would be reproductively isolated from both parent species. B)The two parent species would interbreed and fuse into one species. C)The tetraploids would be selected against. D)The two parent species would recognize each other as mates.

The tetraploids would be reproductively isolated from both parent species.

how long does it take new species to form on Earth

The time required varies considerably

How long does it take new species to form on Earth?

The time required varies considerably. Read examples of both rapid and slow speciation events.

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 have many genes in common. B)The two forms are very similar in coloration. C)The two forms interbreed often in nature, and their offspring have good survival and reproduction. D)The two forms have similar food requirements. E)The two forms live in similar habitats.

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

The two forms interbreed often in nature, and their offspring survive and reproduce well.

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)Reinforcement must be occurring when they winter together. C)They must have strong prezygotic isolating mechanisms to spend winter in such close proximity. D)Their winter habitat has no bearing on their degree of reproductive isolation.

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

A similar control experiment was performed with flies adapted to maltose, and similar results were obtained. What were these control experiments testing?

These control experiments tested whether flies were more likely to choose mates from their own population than from another population adapted to the same medium.

The question refers to the following description. In the ocean, on either side of the Isthmus of Panama, are 30 species of snapping shrimp; some are shallow-water species, others are adapted to deep water. There are 15 species on the Pacific side and 15 different species on the Atlantic side. The Isthmus of Panama started rising about 10 million years ago. The oceans were completely separated by the isthmus about 3 million years ago. Why should deepwater shrimp on different sides of the isthmus have diverged from each other earlier than shallow-water shrimp?

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

True or false? A flood that separates a population of frogs onto opposite sides of a lake is an example of a vicariance event that may result in allopatric speciation.

True

habitat isolation

Two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers

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 gametic reproductive isolating mechanism C)a postzygotic isolating mechanism D)a behavioral reproductive isolating mechanism

a behavioral reproductive isolating mechanism

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, and their beaks begin to change. About twice a year, one or two more birds from the neighboring island arrive. Which of the following effects is most likely to result from the immigration?

a decrease in birds' adaptation to the new food plants

According to the concept of punctuated equilibrium,

a new species accumulates most of its unique features as it comes into existence.

According to the biological species concept, individuals belong to the same species if they can interbreed in nature and produce viable, fertile offspring. Prezygotic and postzygotic barriers ensure that members of different species do not reproduce with one another. This diagram shows some of these barriers along with examples of the barriers at work.

a: prezygotic barriers b: postzygotic barriers c: behavioral isolation d: mechanical isolation e: temporal isolation f: gametic isolation g: reduced hybrid fertility h: two fish species spawn at different depths i: a coral's sperm can't fertilize another's eggs j: offspring of two newts are sterile k: lion-tiger hybrids don't reach maturity

Mass extinctions create conditions that promote _____.

adaptive radiation

The appearance of an evolutionary novelty promotes _____.

adaptive radiation

______ is rapid speciation under conditions in which there is little competition

adaptive radiation

the different finch species found on the Galápagos Islands probably arose as a result of _______.

adaptive radiation

house finches occurred only in western North America until 1930, 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. Which of the following terms best describes the process that had occurred if the two forms did not interbreed when their expanding regions met?

allopatric speciation

which of the following methods is most likely to lead to the production of two species from one ancestral species

allopatrically, after the amxestral species has split into two populations

A hybrid zone is properly defined as

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

The phenomenon of fusion is likely to occur when, after a period of geographic isolation, two populations meet again and

an increasing number of viable, fertile hybrids is produced over the course of generations.

one possible outcome of hybridization is fusion of two species. Which of the following conditions is most likely to increase the probability of fusion of the two species as a result of hybridization

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

According to the biological species concept, for speciation to occur, _____. A)large numbers of genes that affect numerous phenotypic traits must change B)at least one gene, affecting at least one phenotypic trait, must change C)changes to centromere location or chromosome size must occur within the gene pool D)the number of chromosomes in the gene pool must change

at least one gene, affecting at least one phenotypic trait, must change

which of the following statements correctly describes a change that must occur for a new species to arise

at least one gene, affecting one reproductive barrier, must change

which of the following has been shown to cause speciation most rapidly

autopolyploidy

what is a phylogenetic species concept

based on evolutionary history

the original habitat of the north american maggot fly, Rhagoletis pomonella, was native hawthorn trees. About 200 years ago, some populations colonized newly introduced apple trees. The two populations are still classified as subspecies, but sympatric speciation is under way. What has contributed to incident speciation in the maggot fly?

because apples mature more quickly than hawthron fruit, the apple-feeding flies have been selected for more rapid development

Three populations of crickets look very similar, but the males have different courtship songs. If the cricket populations were to contact each other in the wild, the different courtship songs would most likely function as which type of reproductive isolating mechanisms

behavioral

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?

behavioral isolation

There is still some controversy among biologists about whether Neanderthals should be placed within the same species as modern humans or into a separate species of their own. Most DNA sequence data analyzed so far indicate that there was probably little or no gene flow between Neanderthals and Homo sapiens. Which species concept is most applicable in this example?

biological

Which of the various species concepts distinguishes two species based on the degree of genetic exchange between their gene pools?

biological

Dogs (Canis lupus familiaris) and gray wolves (Canis lupus) can interbreed to produce viable, fertile offspring. These species shared a common ancestor recently (in geologic time) and have a high degree of genetic similarity, although their anatomies vary widely. Judging from this evidence, which two species concepts are most likely to place dogs and wolves together into a single species?

biological and phylogenetic

Speciation

can involve changes to a single gene.

Two animals are considered members of different species if they _____.

cannot mate and produce viable, fertile offspring

a team of scientists plan to study divergence of populations and needs to maximize the rate of divergence to see results within the period of grant funding. They will form a new population by taking some individuals from a source population and isolating them so the source and new populations cannot interbreed. Which of the following strategies would maximize the likelihood of seeing divergence between the source and new populations in this study

choosing individuals from one extreme of the source population to form the new popularion and placing the new population in a novel enviornment

The question refers to the following description. 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, 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 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

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.

which of the following factors would be most likely to contribute to allopathic speciation

different mutations begin to distinguish the gene pools of the separatef populations

true or false: a mating between a tetraploid individual and a diploid individual produces biologically fit offspring

false

temporal isolation

form of reproductive isolation in which two populations reproduce at different times

a certain species of salamander was split into two populations by a wide, dry valley, and the population began to diverge from each other. After a period of time, some members of the two populations began to interbreed in a hybrid zone at the southern end of the valley. Only one werk reproductive barriers existed by this time, so the two populations could freely interbreed and re-establish gene flow. Thus outcome in a hybrid zone is known as ______.

fusion

the number cichlid species in Lake Victoria is declining, in part because of predation by Nike perch. Which of the following factors is also likely to contribute to the decline in the number of cichlid species in Lake Victoria

fusion of species

The most likely explanation for the recent decline in cichlid species diversity in Lake Victoria is

fusion.

two juniper trees have overlapping geographic ranges. Pollen grains from one species are unable to germinate and make pollen tubes on female ovules of the other species. which of the following isolating mechanisms keeps the two species separate

gameric isolation

What is the most important factor that holds a gene pool of a species together and prevents speciation?

gene flow

What prevents speciation from occurring in sympatric populations?

gene flow

which of the following factors is the primary criterion for determining species boundaries when applying the biological species concept

gene flow

Which of these should decline in hybrid zones where reinforcement is occurring?

gene flow between distinct gene pools

A windstorm transports a few seeds of a plant species from Island A, where the species is abundant, to Island B, where prior to this event the plant species was not found. The environmental conditions on the two islands are very similar, but the islands are located far away from one another. Over time, a small population of this plant becomes established on Island B. A biologist samples plants on both islands and finds that allele frequencies on Island A differ substantially from allele frequencies on Island B at several genetic loci not known to affect survival or reproduction. Based on this information, the observed genetic changes mostly likely resulted from

genetic drift

which of the following is the first step in allopatric speciation

geographic isolation

The question refers to the following description. 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, 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 14 million years ago. Using only the information provided in the paragraph, which of the following is the best initial hypothesis for how D. santomea descended from D. yakuba?

habitat differentiation

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?

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 in captivity, they interbreed and produce fertile young whose appearance is intermediate between the two parents. In the wild, the two populations remain separate as a result of which of the following factors?

habitat isolation

how many chromosomes would be found in an allopolypoid plant if it's parents had diploid numbers of 2 and 10 respectively

haploid number of 6

The question refers to the following description. 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, 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 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?

hybrid sterility

which of the following conditions is most likely to reinforce isolating mechanisms between two species that occasionally hybridize

hybrids have lower fitness than either parent population

behavioral isolation

isolation between populations due to differences in courtship or mating behavior

The question refers to the following description. 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. If one builds a canal linking a predator-rich pond to a predator-poor pond, then what type(s) of selection should subsequently be most expected among the mosquitofish in the original predator-rich pond, and what type(s) should be most expected among the mosquitofish in the formerly predator-poor pond?

less-intense directional selection; more-intense directional selection

mechanical isolation

which of the following statements about meiosis is correct

meiosis produces cells that differ genetically from the parent cell

which of the following statements best describes unity within a species

members of a given soecies have the potential to interbreed in nature and produce vuable, fertile offspring

You are confronted with a box of preserved grasshoppers of various species that are new to science and have not been described. Your assignment is to separate them into species. There is no accompanying information as to where or when they were collected. Which species concept will you have to use?

morphological

recently a museum scientist discovered a case of preserved grasshoppers that do not resemble any named species. No information about when and where the specimens were collected is available. Which of the following concepts would be most appropriate to use in identifying and naming new specimens

morphological

According to the punctuated equilibria model,

most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species.

what is a biological species concept

not applicabe for extinct species

Two species of tree frogs that live sympatrically in the eastern 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 difference most likely evolved first?

polyploidy

which of the following factors is most likely to produce a reproductive barrier in a single population

polyploidy

which of the following possible causes of speciation is most likely to cause rapid speciation

polyploidy

adaptive radiations on archipelagos represent some of the best-understood speciation events. Why is an ancestral species more likely to give rise to multiple descendent species on an archipelago than on an equal-sized area of mainland

populations in nearby islands are more likely to be genetically isolated than populations that are equally close to one another on the mainland

According to the _____ model, evolution occurs in spurts; species evolve relatively rapidly then remain unchanged for long periods.

punctuated equilibrium

which of the following characteristics are demonstrated by the production of sterile mules after female horses mate with male donkeys

reduced hybrid fertality

The production of sterile mules by interbreeding between female horses (mares) and male donkeys (jacks) is an example of _____. A)reduced hybrid fertility B)hybrid breakdown C)mechanical isolation D)reduced hybrid viability

reduced hybrid fertility

Two species of frogs belonging to the same genus occasionally mate, but the embryos stop developing after a day and then die. Which of the following mechanisms keep the species separate

reduced hybrid viability

The next few questions refer to the following description. 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, 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 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

reinforcement.

which of the following statements best describes the difference between geographic isolation and habitat differentiation ( isolation )?

relative location of two populations as speciation occurs

The difference between geographic isolation and habitat differentiation is the

relative locations of two populations as speciation occurs.

What is the morphological species concept?

relies on similarities in structure

If biological species are defined in terms of reproductive compatibility, which of the following factors determines the formation of a new species?

reproductive isolation

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 and their geographic ranges overlap. Each species eats a different kind of food. None of the species can fly and the balancing organs of males differs among species and are now used in courtship displays. Fly species W produces fertile offspring with species Y, but not with species X or Z. Furthermore, X and Z do not hybridize. Which of the following statements about species W and Y is most likely to be accurate?

species W and Y may fuse into a single specidz if their hybrids remain fedtile over the course of many generations

Theoretically, the production of sterile mules by interbreeding between female horses (mares) and male donkeys (jacks) should

strengthen postzygotic barriers between horses and donkeys.

what is true about sympatric speciation

sympatric speciation can occur in a single generation

The origin of a new plant species by hybridization, coupled with accidents during cell division, is an example of

sympatric speciation.

Beetle pollinators of a particular plant are attracted to its flowers' bright orange color. The beetles not only pollinate the flowers, but they 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?

sympatric speciation; habitat differentiation

in the western US, pronghorn antelopes and domestic cattle often associate with one another in the same open rangeland. In a hypothetical situation, a certain species of flea originally fed only on pronghorn antelopes. Some of these fleas developed a strong preference for cattle blood and mated only with other fleas that also preferred cattle blood. The host mammal can be considered as the fleas' habitat. Which of the following processes most likely occurred if the situation persisted and a new species evolved?

sympatruc speciation and habitat isolation

which term is used to describe populations that live close enough to interbreed

sympatry

what would be the ploidy of the viable gametes produced by a tetraploid individual if nondisjunction of all chromosomes occurred in meiosis I

tetraploid

sympatric speciation is ________

the appearance of a new species in the same area as the parent population

Hybrid zones provide an opportunity to investigate _____.

the evolution of reproductive isolation

Identify the independent variable in this study.

the geographic distance between dusky salamander populations

a subset of the population of birds leaves its habitat on the mainland and colonizes as a nearby island. The birds, after a period of time, become reproductively isolated. The island sinks and the population of birds that lived on the island returns to its original habitat. Which of the following statements about these bird populations is true

the populations will not be able to interbreed because they are different species

Two species of frogs belonging to the same genus occasionally mate, but the offspring fail to develop and hatch. What is the mechanism for keeping the two frog species separate?

the postzygotic barrier called hybrid inviability

Identify the dependent variable in this study.

the reproductive isolation values for pairs of dusky salamander populations

in the oceans on either side of the Isthmus of Panama are 30 species of snapping shrimp, 15 species on the Pacific side and 15 different species on the Atlantic side. Species live at different water depths. Morphological and genetic data show that Atlantic and Pacific species that live at similar depths are sister species. Geological evidence indicates that the Isthmus of Panama started rising about 10 million years ago and the oceans were completely separated by the isthmus about 3 million years ago. Which of the following statements would best explain why the shallow-water sister species are more similar to each other than are the deeper-water species?

the shallow-water sister species have been geographically isolated from each other for a shorter time than the deep-water sister soecies have been

the two soecies reproduce in different geographic area

almost all peppered moths in England were light colored before the industrial revolution. However, some dark forms were collected - the dark color is determined by a single, dominant allele of one gene. The bark of trees became darker during the industrial revolution in areas where heavy coal use in factories caused pollution. By about 1900, approximately 90% of the moths around industrial areas were dark, whereas light colored moths were still abundant elsewhere. Apparently, birds could readily find the light moths against the dark trees in industrial areas and, therefore, were eating more light moths. Recently, use of cleaner fuels has resulted in tree bark becoming lighter again and the dark colored moths have been disappearing. Which of the following statements best explains whether we should consider the forms different species

they are NOT different species - as shown by the fact that they can interbreed

they are different species and postzygitic isolation exists between the two frog species

which of the following statements about autopolypoid individuals is true

they conatin more than two haploid sets of chromosomes

Why did the researchers set up four possible matings for each pair of populations: female A + male A; female B + male B; female A + male B; female B + male A?

to compare the proportion of successful matings within populations to the proportion of successful matings between populations

true or false: a flood that separates a population of frogs onto opposite sides of a lake is an example of a vicariance event that may result in allopathic speciation

true

which of the following provides an example of a mechanical isolation as a prezygotic barrier

two snails havs shells that spiral in different directions

what is a shared concept for morphological, phylogenetic, and biological species

used by scientists in classification

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