Question 1

The difference between geographic isolation and habitat differentiation is the

Accepted Answer

Geographic isolation refers to physical separation of two populations, whereas habitat differentiation refers to the evolution of differences in habitat use or preference within one population. In other words, geographic isolation involves the relative locations of two populations as speciation occurs, while habitat differentiation does not.

Question 2

Prezygotic barriers include all of the following, except for

Accepted Answer

E

Question 3

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?

Accepted Answer

The fact that the two species of frogs occasionally mate but the offspring fail to develop and hatch suggests that there is a postzygotic barrier preventing successful reproduction. Specifically, the offspring are inviable, which is a type of postzygotic barrier known as hybrid inviability. This mechanism helps to keep the two frog species separate by preventing the formation of viable hybrid offspring.

Question 4

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

Accepted Answer

Sterile mules result from the mating of horses and donkeys, which are different species. This interbreeding does not result in the formation of a new species. However, it can strengthen postzygotic barriers between the two parental species, as the sterile mules produced by this mating cannot reproduce. This can result in reduced interbreeding between horses and donkeys, as the production of sterile offspring represents a reproductive dead end for both parental species.

Question 5

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?

Accepted Answer

Dogs and wolves can interbreed to produce viable, fertile offspring, which indicates that they belong to the same biological species. They also share a recent common ancestor and have a high degree of genetic similarity, which suggests that they belong to the same phylogenetic group. Therefore, the biological and phylogenetic species concepts are the most likely to place dogs and wolves together into a single species.

Question 6

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?

Accepted Answer

Habitat isolation involves two closely related species that occupy different habitats, which prevents them from mating with each other. Similarly, dog breeders keep their dogs of different breeds apart, which could be considered as occupying different habitats within the breeder's breeding facility. Therefore, the maintenance of purity of dog breeds through isolation is most similar to habitat isolation. The other options, such as reduced hybrid fertility, hybrid breakdown, mechanical isolation, and gametic isolation, involve different mechanisms that prevent gene flow between two populations/species.

Question 7

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

Accepted Answer

The correct terms are "sympatric species" because the species have overlapping ranges, indicating they live in the same geographic area, and "prezygotic isolation" because the inability of pollen grains from one species to germinate on the ovules of another species prevents fertilization from occurring, which is a barrier that acts before the formation of a zygote.

Question 8

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?

Accepted Answer

The only feasible way to identify species when there is no accompanying information regarding their place or time of collection is to use morphological species concept, which involves identifying species based on their physical characteristics.

Question 9

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

Accepted Answer

The scenario describes a situation where fleas develop a preference for a different host (cattle instead of pronghorns) and mate only among themselves, leading to reproductive isolation (1), which is a prezygotic barrier (4). This situation occurs within the same geographical area (sympatric speciation, 2) without physical separation, but with a behavioral change that leads to a different use of the habitat (the host animal), effectively creating habitat isolation (3).

Question 10

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.

Accepted Answer

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 but are reproductively isolated from members of other species. Therefore, statement I is correct. Statement II is incorrect because the biological species concept is only applicable to extant (living) organisms, not extinct forms of life. Statement III is correct as the biological species is the largest unit of population in which individuals are able to interbreed and exchange genetic material, leading to successful reproduction.

Question 11

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?

Accepted Answer

The most applicable species concept in this example is the biological species concept, which defines a species as a group of organisms that can interbreed and produce viable, fertile offspring. The lack of gene flow between Neanderthals and Homo sapiens suggests that they were reproductively isolated and therefore different species, according to this concept. The other concepts (phylogenetic, ecological, and morphological) are not as relevant in determining whether Neanderthals and Homo sapiens were separate species.

Question 12

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

Accepted Answer

The answer of What is true of the flightless cormorants...

Question 13

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

Accepted Answer

The answer of Among known plant species, which of these...

Question 14

What is true of macroevolution?

Accepted Answer

Macroevolution refers to evolutionary changes above the species level, such as the origin of new groups of organisms or major evolutionary patterns. It is distinct from microevolution, which refers to changes in the gene pool of a population from one generation to the next. Options A, C, D, and E are incorrect because they do not accurately define macroevolution.

Question 15

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 is applicable?

Accepted Answer

Mechanical isolation refers to physical or structural differences in reproductive organs or structures that prevent mating or fertilization between species. In this case, pollen grains from one species are unable to make pollen tubes on female ovules of the other species, suggesting a physical barrier to fertilization, which fits the definition of mechanical isolation.

Question 16

When male horses (stallions)and female donkeys (jennets)mate, they produce a sterile hybrid called a hinny. Hinnies occur much less frequently than do mules, but are just as healthy and robust as mules. Logically, which of the following best accounts for the relative rarity of hinnies, and what kind of prezygotic isolating mechanism is at work here?

Accepted Answer

Stallions and jennets being choosier about their mating partners than mares and jacks is an example of behavioral isolation, a prezygotic isolating mechanism.

Question 17

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

Accepted Answer

The biological species concept distinguishes two species based on the degree of genetic exchange between their gene pools. According to this concept, a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring but do not successfully interbreed with other such groups. This concept emphasizes reproductive isolation as the key factor that separates one species from another.

Question 18

Two closely related populations of mice have been separated for many generations by a river. Climatic change causes the river to dry up, thereby bringing the mice populations back into contact in a zone of overlap. Which of the following is not a possible outcome when they meet?

Accepted Answer

Option A, B, D, and E are possible outcomes when two closely related populations of mice meet after being separated for many generations. However, the possibility of producing inferior hybrids in the region of overlap that subsequently produce progressively superior hybrids over several generations is not supported by any known biological mechanism. In general, hybridization can result in various outcomes depending on several ecological, genetic, and behavioral factors.

Question 19

Rank the following from most general to most specific. 1. gametic isolation
2. reproductive isolating mechanism
3. pollen-stigma incompatibility
4. prezygotic isolating mechanism

Accepted Answer

- Reproductive isolating mechanism is the most general, as it encompasses any mechanism that prevents interbreeding between different species.
- Prezygotic isolating mechanism is more specific, as it refers to mechanisms that prevent mating or fertilization from occurring (such as gametic isolation).
- Pollen-stigma incompatibility is even more specific, as it refers to a particular mechanism of prezygotic isolation.
- Gametic isolation is the most specific, as it specifically refers to the inability of sperm from one species to fertilize eggs of another species. 
Therefore, the correct order from most general to most specific is 2, 4, 1, 3. Choice B is the only option that follows this order.

Question 20

What does the biological species concept use as the primary criterion for determining species boundaries?

Accepted Answer

The biological species concept defines a species as a group of organisms that can interbreed and produce viable, fertile offspring, and gene flow (or lack thereof) is the primary criterion used to determine species boundaries. If two groups of organisms do not interbreed, or if they do but their offspring are not viable or fertile, they are considered separate species. The other options (A, B, D, and E) may be used as secondary criteria to support the biological species concept but are not the primary criterion used to determine species boundaries.

Quiz 24: The Origin of Species