Question 1

Which of these evolutionary trees represents the situation described in the previous paragraph? (Note: Yakuba (I) represents the island population, and yakuba (M) represents the mainland population.)

Accepted Answer

The answer of Which of these evolutionary trees represents the...

Question 2

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

Accepted Answer

Gene flow is the transfer of genetic material (alleles) from one population to another. The largest unit within which gene flow can readily occur is a species, as individuals within a species have the potential to interbreed and exchange genes. Populations within a species may have different gene frequencies due to factors such as geographic isolation, natural selection, or genetic drift. However, if individuals from different populations of the same species come into contact and reproduce, gene flow can occur and potentially homogenize the gene pool. Beyond the species level, interbreeding and gene flow become less common or impossible due to reproductive barriers.

Question 3

If a speciation event occurred on Sao Tomé, producing D. santomea from a parent colony of D. yakuba, then which of the following terms applies (apply)? I. macroevolution
II allopatric speciation
III) sympatric speciation

Accepted Answer

The answer of If a speciation event occurred on Sao...

Question 4

The next few questions refer 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?

Accepted Answer

With the canal linking the two ponds, there will be less-intense directional selection in the predator-rich pond because there is now gene flow from the predator-poor pond. This means that the mosquitofish in the predator-rich pond will have more genetic diversity and less intense selective pressures. Conversely, there will be more-intense directional selection in the formerly predator-poor pond because now the predators from the predator-rich pond can enter the formerly predator-poor pond, putting selective pressure on the mosquitofish to evolve adaptations for escaping or avoiding predators.

Question 5

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

Accepted Answer

Allopolyploid species C arises from the hybridization of two different species A and B, which results in a hybrid with chromosomes derived from both parent species. The diploid number in species C will be the sum of the diploid numbers in A and B. Therefore, the diploid number in species C would be 12 + 16 = 28.

Question 6

Which conclusion can be drawn from this evolutionary tree?

Accepted Answer

The answer of Which conclusion can be drawn from this...

Question 7

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

Accepted Answer

The process of reinforcement occurs when there is natural selection against hybrids, leading to a reduction in hybridization and an increase in the reproductive isolation of the two parental species. This is consistent with the conditions described in the question, where hybrids are poorly adapted to conditions in the hybrid zone and fewer hybrids are produced over time. Therefore, reinforcement is the most likely outcome.

Question 8

The next few questions refer 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.
-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

Accepted Answer

Natural selection has played a role in selecting for different swimming abilities in response to different predator environments, leading to divergence between mosquitofish populations. Sexual selection has also played a role in promoting breeding preferences between the different populations. Improved gene flow would work against divergence, while bottleneck effect and founder effect would decrease genetic variation but may not necessarily lead to divergence between populations.

Question 9

The next few questions refer 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

Accepted Answer

Directional selection for increased speed (1) may help predators catch faster mosquitofish, while a change in hunting behavior that replaces visual cues with tactile cues (3) may help predators hunt at night when visual cues are less effective. Additionally, a change in hunting behavior that eliminates speed in favor of better camouflage (4) would allow predators to use an ambush strategy and catch mosquitofish that way. Therefore, choices 1, 3, and 4 provide potential adaptations that would help predatory fish survive in ponds with faster mosquitofish.

Question 10

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

Accepted Answer

Gene flow between populations would prevent allopatric speciation as it allows for the mixing of gene pools and the spread of advantageous alleles between populations. In allopatric speciation, populations become geographically isolated, which restricts gene flow and allows for genetic divergence over time. All of the other factors listed (A, B, C, and D) contribute to allopatric speciation by limiting gene flow, inducing genetic drift or mutations, or creating divergent selection pressures.

Question 11

Bird guides once listed the myrtle warbler and Audubon's warbler as distinct species. Recently, these birds have been reclassified 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?

Accepted Answer

The fact that the two forms interbreed and produce viable offspring indicates that they are not reproductively isolated and are likely the same species. This would be a strong piece of evidence for reclassifying them as one species. The other choices do not necessarily provide clear evidence for their reclassification.

Question 12

The next 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?

Accepted Answer

Deepwater shrimp on either side of the isthmus have been geographically isolated from each other for a longer time because they were already adapted to their respective deep water habitats before the isthmus formed, while shallow-water shrimp likely colonized their respective habitats after the isthmus formed. Therefore, deepwater shrimp had a head start in diverging from each other.

Question 13

The next few questions refer 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.
-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?

Accepted Answer

Building a canal that allows only mosquitofish to move freely between the two ponds would promote fusion by enabling natural migration and mixing without altering the predator dynamics of either pond.

Question 14

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

Accepted Answer

The genetic similarity between island and mainland D. yakuba suggests a more recent common ancestry between these populations than between island D. yakuba and D. santomea. This implies that the current island D. yakuba population came from a separate, later colonization event, distinct from the one that gave rise to D. santomea.

Question 15

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.
-Which of the following reduces gene flow between the gene pools of the two species on Sao Tomé, despite the existence of hybrids?

Accepted Answer

Hybrid sterility reduces gene flow between the gene pools of the two species on Sao Tomé because the male hybrids are sterile and cannot produce viable offspring, limiting the exchange of genetic material between the two species.

Question 16

Which of these five species is the extant (i.e., not extinct) species that is most closely related to species X, and why is this so?

Accepted Answer

The species that is most closely related to another species is the one that shared a common ancestor with it most recently. Choices B, C, and D are incorrect because they either do not specify this crucial detail or add irrelevant information. Choice E is incorrect because the question assumes the existence of a phylogenetic tree or some form of lineage information that allows for the determination of relationships based on common ancestry.

Question 17

According to the punctuated equilibria model,

Accepted Answer

The punctuated equilibria model suggests that new species accumulate their unique features relatively quickly as they come into existence, and then change very little for the rest of their existence as a species. This is in contrast to the gradualism model, which suggests that species evolve slowly and gradually over time. The punctuated equilibria model does not suggest that natural selection is unimportant or that speciation is usually due to a single mutation.

Question 18

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?

Accepted Answer

The courtship rituals of different species of fruit flies represent behavioral isolation as they have evolved different behaviors associated with mating that prevent interbreeding between them.

Question 19

The next few questions refer 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.
-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?

Accepted Answer

Behavioral isolation is the type of reproductive isolation that operates to keep the mosquitofish isolated, as they exhibit exclusive breeding preferences even when placed together in the same body of water.

Question 20

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?

Accepted Answer

Habitat differentiation is the best initial hypothesis for how D. santomea descended from D. yakuba, as the two species inhabit different elevations on the same island, suggesting that adaptation to different habitats (lowlands vs. high elevations) could have driven their divergence.

Quiz 22: The Origin of Species