Question 1

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?

Accepted Answer

Reduced hybrid viability is the correct answer because it refers to the situation where hybrid offspring fail to develop properly or die at an early stage, as described in the scenario with the frog embryos.

Question 2

Which of the following statements best describes a limitation of the biological species concept?

Accepted Answer

The biological species concept defines species based on reproductive isolation, which cannot be assessed in fossils since we cannot observe their reproductive behaviors or capabilities.

Question 3

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?

Accepted Answer

The two populations remain separate due to habitat isolation, as the unsuitable habitat between them prevents them from coming into contact and interbreeding in the wild.

Question 4

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

Accepted Answer

The biological species concept primarily uses reproductive isolation, of which gene flow is a critical component, to determine species boundaries. It posits that species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups.

Question 5

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 occurs when two species live in the same area but encounter each other rarely, or not at all, because they occupy different habitats. This is similar to dog breeders keeping dogs of different breeds apart to prevent them from mating, as it involves physical separation to prevent different groups from interbreeding.

Question 6

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?

Accepted Answer

The ability to interbreed and produce fertile offspring is a key criterion for defining organisms as belonging to the same species, indicating that the light and dark forms of the peppered moth are not different species.

Question 7

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 mechanism?

Accepted Answer

Different courtship songs in crickets act as a behavioral isolating mechanism, preventing mating between individuals of different populations by influencing mate choice based on specific behaviors, in this case, the unique songs of the males.

Question 8

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

Accepted Answer

Reproductive isolation is the key factor in the formation of new species according to the biological species concept, as it prevents gene flow between populations, leading to speciation.

Question 9

The common edible frog of Europe is a hybrid between two named 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 rarely produce offspring. Which of the following statements is the best inference about the two Rana species?

Accepted Answer

Prezygotic isolation mechanisms prevent mating or fertilization between species, while postzygotic isolation mechanisms occur after fertilization, often resulting in the production of infertile offspring. The fact that hybrids between Rana lessonae and Rana ridibunda rarely produce offspring when they mate among themselves suggests that postzygotic isolation exists between the two frog species, as their hybrid offspring are likely infertile or have reduced fertility. This supports the idea that they are indeed different species according to the biological species concept, which defines species based on reproductive isolation.

Question 10

Two juniper trees (Juniperus scopulorum and J. monosperma) have overlapping geographic ranges. 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. Which of the following isolating mechanisms keeps the two species separate?

Accepted Answer

Gametic isolation is a prezygotic barrier where the gametes (e.g., pollen and ovules in plants) of two different species meet but are unable to fuse to form a zygote. In this case, the pollen grains from one juniper species cannot germinate on the ovules of the other species, preventing fertilization and thus maintaining species separation.

Question 11

Which of the following statements best describes unity within a species?

Accepted Answer

Members of a given species have the potential to interbreed in nature and produce viable, fertile offspring. This is a fundamental concept in biology that defines a species according to the biological species concept.

Question 12

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

Accepted Answer

Mules, which are the offspring of a female horse and a male donkey, are typically sterile, demonstrating reduced hybrid fertility. This sterility is a postzygotic barrier that prevents the hybrids from reproducing, even though they can survive and often thrive.

Question 13

The diagram represents the splitting of one population into two separate lineages that become more different over time (the distance between the two lines represents the amount of difference between the two lineages). Which of the following statements about the two lineages is most accurate?

Accepted Answer

The answer of  The diagram represents the splitting of...

Question 14

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

Accepted Answer

Mechanical isolation occurs when physical differences between species prevent successful mating, as in the case of snails with shells that spiral in different directions, which can physically impede mating.

Question 15

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, defining species in terms of reproductive isolation.

Question 16

Lions and tigers sometimes breed in zoos, but hybrids have not been seen in nature and even in zoos they do not reproduce well. Which of the following statements is the best conclusion that can be derived from this information?

Accepted Answer

The biological species concept defines species based on the ability to produce viable, fertile offspring. Since lions and tigers do not reproduce well even in captivity, and hybrids are not found in nature, it supports the idea that they are indeed separate species according to this concept.

Question 17

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 species concepts would be most appropriate to use in identifying and naming the new specimens?

Accepted Answer

The morphological species concept would be most appropriate in this scenario because it relies on the physical characteristics and form of the organisms, which is the primary information available from the preserved specimens. Other concepts like biological, genetic, and ecological require more information about the organisms' reproduction, genetic makeup, or ecological roles, which is not available in this case.

Question 18

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

Accepted Answer

Hybrid breakdown is a postzygotic barrier where the first-generation hybrids are viable and fertile, but when they mate, the next generation is feeble or sterile.

Question 19

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, species X and species Y, overwinter together in mixed flocks in Costa Rica. In spring, species X goes to the east coast of North America, and species Y goes to the west coast. Which of the following factors most likely keeps these species separate?

Accepted Answer

The two species reproduce in different geographic areas, which is a geographic isolation mechanism preventing them from interbreeding.

Question 20

Which of the following statements best describes macroevolution?

Accepted Answer

Macroevolution refers to evolutionary changes that occur at or above the level of species, encompassing the grand scale of evolutionary transformations, such as the emergence of new species, genera, families, and higher taxonomic groups over geological time. It contrasts with microevolution, which involves smaller evolutionary changes (typically described as changes in allele frequencies) within a species or population over a shorter period.

Quiz 24: Species and Speciation