Question 1

Which examples would be considered different species under the biological species concept? Check all that apply.

Accepted Answer

The answer of Which examples would be considered different species...

Question 2

Punctuated equilibrium proposed by Eldredge and Gould in 1972 is an evolutionary process that involves

Accepted Answer

Punctuated equilibrium proposes that evolution occurs in spurts of rapid change followed by periods of stasis, where there is little or no change. This is in contrast to the idea of gradualism, where evolution occurs slowly and steadily over time with no periods of stasis. The fossil record provides evidence for this pattern of evolution, with many species appearing suddenly in the record and remaining relatively unchanged for long periods of time.

Question 3

Studies of snapping shrimp on either side of the Isthmus of Panama have shown that each Caribbean shrimp species is more closely related to a Pacific shrimp species than it is to any other Caribbean shrimp species.The most likely explanation for this result is

Accepted Answer

The fact that each Caribbean shrimp species is more closely related to a Pacific shrimp species than it is to any other Caribbean shrimp species suggests that snapping shrimp species in each ocean diverged prior to the formation of the Isthmus of Panama. If they had diverged after the formation of the Isthmus, we would expect each Caribbean shrimp species to be more closely related to other Caribbean shrimp species than to any Pacific shrimp species. The other options are unlikely explanations for this result.

Question 4

The hundreds of species of Drosophila in Hawaii exhibit different mating rituals.This isolating mechanism is

Accepted Answer

The different mating rituals exhibited by the hundreds of species of Drosophila in Hawaii is a behavioral isolating mechanism, which is a type of prezygotic isolation.

Question 5

A virgin pine forest covers a valley,and one of the inhabitants is a red squirrel species.A large volcanic eruption occurs and separates the valley with a huge lava flow,thus producing two populations of squirrels.What must occur for the two populations of squirrels to be considered separate species?

Accepted Answer

For two populations to be considered separate species, they must be reproductively isolated from each other, meaning they cannot interbreed to produce viable offspring. This can happen through several mechanisms, such as geographic isolation (where the two populations are physically separated by a barrier like a lava flow), behavioral isolation (where the two populations have different mating behaviors), or genetic isolation (where the two populations have diverged genetically to the point where they cannot produce viable offspring). Of the given choices, only E addresses this requirement for speciation.

Question 6

The biological species concept of Ernst Mayr cannot be applied to

Accepted Answer

The biological species concept of Ernst Mayr defines a species as a group of actually or potentially interbreeding populations that are reproductively isolated from other such groups. This definition does not apply to asexually-reproducing organisms, as they do not reproduce sexually and therefore cannot interbreed with other populations to create distinct species.

Question 7

Select all of the following that are postzygotic isolating mechanisms.

Accepted Answer

Postzygotic isolating mechanisms refer to barriers that occur after fertilization, preventing hybrids from passing on their genes. Sterility of hybrids (A), abnormal development of hybrids (B), and failure of hybrids to establish in nature (C) are all examples of postzygotic barriers. Choice D is incorrect because it describes a prezygotic barrier, where hybrids cannot be formed in the first place.

Question 8

Select the concepts emphasized by Ernst Mayr's biological species concept.Check all that apply.

Accepted Answer

The biological species concept, as proposed by Ernst Mayr, emphasizes that a species is a group of interbreeding natural populations that are reproductively isolated from other such groups (D), meaning they cannot produce fertile offspring with members of other species. It also stresses the importance of the production of fertile offspring within the species (B), as this is a key mechanism through which species maintain their distinctiveness over time.

Question 9

Two bird species have different mating calls,occupy different habitats in nature,and when they hybridize,the hybrids are infertile.Which isolating mechanisms maintain these species?

Accepted Answer

The different mating calls represent behavioral isolation, occupying different habitats represents ecological isolation, and the infertility of hybrids is an example of postzygotic barrier, specifically hybrid sterility. These mechanisms work together to maintain the species as distinct.

Question 10

Scientists studying a group of related bird species on an island archipelago discover that these species are always more closely related to each other within an island than they are between any two islands.The most likely explanation for this result is that

Accepted Answer

The pattern suggests that one original species colonized each island and then evolved into distinct species on that island through character displacement. This would lead to the relatedness between species being highest within an island and decreasing as you compare species between islands. Option A suggests that each species evolved independently on each island, which would not explain the consistent pattern observed. Option C suggests that each species became reproductively isolated on different islands, but this does not explain why they are more closely related within an island. Option D suggests that many ancestral species colonized each island, which may be a possibility, but the pattern observed suggests a single colonizing species.

Question 11

Two populations that inhabit the same area but remain genetically distinct can best be called

Accepted Answer

The answer of Two populations that inhabit the same area...

Question 12

Very rapid speciation occurred when cichlid fishes were isolated in Lake Victoria.Widespread extinction was dramatically seen when

Accepted Answer

The predatory fish that were introduced into Lake Victoria caused widespread extinction of cichlid fish species. This suggests that predatory pressure was a major factor in the rapid speciation of cichlid fishes, as well as the extinction of those species that could not adapt to new predator populations.

Question 13

The sunflower species Helianthus anomalus is thought to have been formed by hybridization between the sunflower species H.petiolaris and H.annuus because it contains a set of chromosomes from both parental species.H.anomalus is most likely an example of instantaneous speciation through

Accepted Answer

The formation of H. anomalus through hybridization between two different species, followed by a doubling of the chromosome number (allopolyploidy), is known as instant speciation. This rapid process results in a new species with a unique combination of characteristics.

Question 14

The most common mechanism for sympatric speciation in plants is

Accepted Answer

Polyploidy, or the duplication of an organism's entire set of chromosomes, is a common mechanism for sympatric speciation in plants. This can occur due to errors in cell division during meiosis, resulting in a new plant species that can no longer interbreed with the parent species. Geographic isolation, spontaneous mutation, punctuated equilibrium, and disruptive selection are all mechanisms for speciation, but they are less common in plants than polyploidy.

Question 15

Two hundred years ago,the fly species Rhagoletis pomonella only laid its eggs on fruit of the hawthorn tree.Today,different "host races" of R.pomonella lay their eggs on hawthorns OR apples.Apples occur within the range of hawthorns,so divergence between apple flies and hawthorn flies could be the first step in sympatric speciation.Choose the evidence that would suggest that R.pomonella is currently undergoing sympatric speciation.Check all that apply.

Accepted Answer

A) and B) suggest reproductive isolation mechanisms are in place, which is a key factor in sympatric speciation. A) indicates prezygotic isolation due to mating preferences, and B) suggests temporal isolation due to different emergence times.

Question 16

Adaptive radiation is best described as the

Accepted Answer

Adaptive radiation refers to the process by which a single ancestral species rapidly diversifies into a group of closely related species that are adapted to different ecological niches. These species share a recent common ancestor and have evolved through natural selection and adaptation to different selective pressures within their respective habitats.

Question 17

In the southeastern U.S.,two species of wild lettuce (Lactuca)do not usually form hybrids,because they bloom at different seasons.The means of isolation appears to be

Accepted Answer

The fact that the two species of wild lettuce (Lactuca) do not usually form hybrids because they bloom at different seasons suggests that their means of isolation is prezygotic (preventing the formation of zygotes) and temporal (related to timing). Therefore, option B is the best choice.

Question 18

Lake Victoria is famous for its variety of cichlid fishes.In fact,they offer the most diverse assembly of vertebrates presently known to science.One trait that scientists have focused on as one possible reason for their adaptability is

Accepted Answer

The presence of a second set of jaws in their throats is a trait unique to cichlid fishes that allows them to preadapt and exploit different food resources, making them highly adaptable to changing environments.

Question 19

Check all that apply: Members of the same biological species can

Accepted Answer

The answer of Check all that apply: Members of the...

Question 20

Prezygotic mechanisms lead to reproductive isolation by preventing the formation of

Accepted Answer

The answer of Prezygotic mechanisms lead to reproductive isolation by...

Quiz 22: The Origin of Species