Question 1

An ancestral population is split into two different groups, and they no longer interbreed after separation. Which of the following CORRECTLY describes the number of genetic differences that would be seen between the two populations?

Accepted Answer

The answer of An ancestral population is split into two...

Question 2

Flower A blooms in June while flower B, a close relative of A, blooms in August. A researcher is raising a population of flower B in a controlled growth chamber. Over time the researcher manipulated the day length in the growth chamber and eventually manages to induce some individuals of flower B to bloom in June. The researcher finds that she can cross these individuals with flower A individuals and they produce viable, fertile offspring. What can she conclude about flower A and flower B?

Accepted Answer

The fact that flower A blooms in June while flower B blooms in August suggests that they are temporally reproductively isolated from each other. However, the researcher was able to manipulate the day length in the growth chamber and induce some individuals of flower B to bloom in June. This suggests that the difference in blooming time is not due to genetic incompatibility between A and B, and that they are not pre-zygotically isolated from one another. The fact that the crosses between the June-blooming individuals of B and A produced viable, fertile offspring suggests that A and B are not a good example of separate species but rather a case of sub-species or ecotypes.

Question 3

Consider the two phylogenies below of five species of related flowers that hold nectar as a reward for their pollinators, five related species of moths, in their spur.  The similar pattern of the phylogenies suggests the characteristics coevolved with one another. Which of the following is an accurate statement reflecting the figure above?

Accepted Answer

The similar pattern in the phylogenies suggests coevolution, where the spur-length of the flower species and the tongue-length of the moth species evolved together as a result of selective pressures from one another. Co-speciation can occur in mutualistic relationships, such as the one between these flowers and moths. Option A is incorrect because allopatric speciation does not necessarily imply coevolution. Option C is incorrect because co-speciation can occur in a variety of relationships, not just host-parasite ones. Option D is incorrect because the phylogenies do not represent the variation within a population but rather the evolutionary relationships between species.

Question 4

Which of the following statements is TRUE regarding the biological species concept?

Accepted Answer

The biological species concept defines a species as a group of organisms that can interbreed and produce viable offspring. This concept can be difficult to test in certain organisms with long generation times, as it can take many generations to observe whether or not they can successfully interbreed.

Question 5

A researcher is trying to determine whether different populations of asexually reproducing bacteria belong to the same species. What concept will be MOST helpful in making this determination?

Accepted Answer

The ecological species concept will be most helpful because it defines species in terms of their ecological niches, focusing on unique adaptations to particular roles in a biological community. This is particularly useful for asexually reproducing organisms, where the biological species concept, which emphasizes reproductive isolation, does not apply.

Question 6

Imagine that a zoo in Sri Lanka has started an elephant-breeding program. Zookeepers have introduced an Indian and Sri Lankan elephant into the same enclosure. What will be the result of this mating?

Accepted Answer

Indian and Sri Lankan elephants are considered to be the same species, Elephas maximus. These elephants can mate and produce fertile offspring, which have been observed in both the wild and captivity. Therefore, introducing an Indian and Sri Lankan elephant into the same enclosure can result in the production of viable, fertile offspring, demonstrating that they are not reproductively isolated and are members of the same species.

Question 7

New species can form through allopatric or sympatric speciation. Which of the following mechanisms will act more strongly on populations that are initially separated in allopatry than on those initially separated in sympatry?

Accepted Answer

Genetic drift acts more strongly on populations that are initially separated in allopatry because these populations are often small and isolated, making them more susceptible to random changes in allele frequencies.

Question 8

Male birds of different species sing species-specific songs to attract mates. Females only mate with males that sing their species-specific song. This is an example of:

Accepted Answer

The answer of Male birds of different species sing species-specific...

Question 9

What conditions must be met if we are to establish that a species arose via sympatric speciation? Give an example in which these conditions are met.

Accepted Answer

The answer of What conditions must be met if we...

Question 10

A single species of fish, the three-spined spinyback, once inhabited a large lake. At some point in the lake's history, lava flowed from a nearby volcano into the lake cutting it into three completely isolated mini-lakes. Despite the heat from the lava, a few individuals from the original population of spinyback survive in each mini-lake. Three million years later, a researcher finds that each mini-lake is inhabited by its own species of spinyback. Which of the following figures MOST closely reflects how the three species of spiny back are related to one another?

Accepted Answer

The answer of A single species of fish, the three-spined...

Question 11

A large population of mice (2000 individuals) lives in an area dominated by small shrubs in the desert. When the population size got too high, a small group of 6 individuals left and colonized an area adjacent to the original population's home, but this area is primarily dominated by trees instead of shrubs. There is no gene flow between the dispersers and the original population. A researcher sequenced the genomes of representative individuals from both populations and found substantial genetic differences between them. Which of the following would MOST account for the amount of genetic differences observed?

Accepted Answer

Since the small group that dispersed from the larger population is a bottleneck population, it will have reduced genetic diversity. This means that it is more prone to genetic drift, which can cause divergence over time. In contrast, the larger population will have more genetic diversity and genetic drift will have a smaller effect on overall genetic variation. Consequently, the small population that dispersed from the larger population will have diverged more than the larger population over time.

Question 12

Several species of fireflies are active on the same summer nights in the same fields. Males and females recognize one another by their distinctive flashing patterns. This is an example of what kind of reproductive isolation?

Accepted Answer

This is an example of pre-zygotic reproductive isolation because it occurs before the formation of a zygote. The specific type of isolation being exhibited is behavioral isolation because the fireflies are not able to mate with individuals that do not have the correct flashing pattern.

Question 13

All members of a species can in principle mate with members of the same species but of the different sex. Two populations would not be considered part of the same species if they do not actively breed (even if they potentially could).

Accepted Answer

The biological species concept defines species based on the ability to interbreed and produce fertile offspring, not on whether they actively do so in nature. Two populations might not interbreed due to geographical, behavioral, temporal, or ecological barriers, but they can still be considered the same species if they are capable of interbreeding under natural conditions.

Question 14

When we look at islands across the planet (think the islands of the Galápagos and Hawaii) we see that there are a remarkable number of island endemic species, species that are found nowhere else. What is a possible explanation for this observation?

Accepted Answer

Island isolation promotes allopatric speciation, which occurs when a population is isolated geographically from a main population, allowing for genetic divergence and ultimately leading to the formation of a new species. The isolation of islands is a common mechanism for allopatric speciation to occur, leading to the evolution of unique island endemic species.

Question 15

If two populations are reproductively isolated from one another (like certain populations of Russian warblers), they must be genetically isolated from each other and therefore cannot belong to the same species.

Accepted Answer

Reproductive isolation is a key mechanism in the process of speciation, but it does not immediately imply that two populations are genetically isolated to the extent that they cannot belong to the same species. Populations can experience periods of reproductive isolation and still interbreed under certain conditions or through mechanisms like hybridization, maintaining genetic flow between them. The concept of a species is complex and can encompass populations that are currently reproductively isolated but still share enough genetic similarity to be considered the same species.

Question 16

The example of speciation via vicariance given in Figure 22.7 focuses on the impact of the formation of the isthmus of Panama on the populations of snapping shrimp living in the shallow waters of the West Caribbean and East Pacific. Would you expect to see a similar pattern of Pacific/Caribbean sister species in other shallow-water organisms?   Photo source: Dr. Arthur Anker, National University of Singapore, Singapore.

Accepted Answer

The answer of The example of speciation via vicariance given...

Question 17

A researcher finds two closely related species of rodent, A and B, living sympatrically on a coastal peninsula. Geological analysis suggests that higher sea levels in the past have occasionally cut off parts of the peninsula-with the lower parts of the peninsula being under water and higher parts becoming separate islands. Do you think species A and B arose sympatrically or allopatrically? Explain your answer.

Accepted Answer

The answer of A researcher finds two closely related species...

Question 18

The graph in Figure 22.9, below, shows that the extent of the adaptive radiation of the Galápagos finches is correlated with the number of islands present in the archipelago. What can be concluded from the graph?

Accepted Answer

The graph shows a correlation between the number of islands present in the Galápagos archipelago and the extent of adaptive radiation of the finches. This suggests that the availability of opportunities for geographic isolation (i.e. being separated by water) is a key component of the speciation process. Therefore, choice C is the best answer. Choices A, B, D, and E are incorrect because they do not directly relate to the information presented in the graph.

Question 19

Which of the following statements is TRUE regarding hybridization?

Accepted Answer

All the statements provided are true regarding hybridization. Hybridization is more common in plants than in animals, involves the transfer of genetic material between similar species, can be subject to natural selection acting against hybrid offspring, and can result in fertile offspring, although this is not always the case.

Question 20

Horses and donkeys can interbreed, but their offspring (mules) are infertile. This is an example of what kind of reproductive isolating mechanism?

Accepted Answer

This is an example of post-zygotic reproductive isolation because the offspring (mules) are produced, but they are infertile due to genetic incompatibility between horses and donkeys.

Quiz 22: Species and Speciation