Question 1

Imagine that a researcher discovers two new similar species of bats in the same geographic area. Amazingly, one of these species preys upon insects during the day. The other species-as one would expect-is nocturnal and only feeds during the night. These two bat species would be considered to be _____ separated.

Accepted Answer

The two species of bats are separated temporally because one feeds during the day and the other feeds during the night. This temporal separation reduces competition for resources between the two species, allowing both to coexist in the same geographic area. Allopatric separation refers to species that are separated geographically, while energetic and peripatric separation are not applicable in this scenario.

Question 2

Imagine a very deep lake with multiple species of fish. The lake has many different regions (i.e., shallow water with high light penetrance, deep water with low light penetrance). A phylogeny of the fish shows that they have all descended from a common ancestor. Which of the following is the MOST likely cause of speciation in fishes in this lake?

Accepted Answer

The fact that the lake has multiple regions means that there are potentially varying ecological niches and selection pressures. This, combined with the phylogenetic evidence of a common ancestor, suggests that speciation likely occurred through sympatric mechanisms, where new species evolved in the same geographic area due to ecological divergence or other factors such as mate selection. Allopatric speciation, where populations are geographically separated, and peripatric speciation, where a few individuals from a larger population colonize a new area, are less likely scenarios in this context.

Question 3

If two individuals from different species attempt to mate but fertilization fails to occur, this is likely the result of _____ factors. However, if such a mating produces a zygote that fails to form a viable embryo, this is likely the result of _____ factors.

Accepted Answer

Pre-zygotic factors prevent the fertilization of gametes from different species, such as differences in reproductive structures or mating behaviors. Post-zygotic factors occur after fertilization, such as problems with embryonic development or reduced fitness of the hybrid offspring.

Question 4

Two species of frog mate in the same pond. One breeds in early summer and one in late summer. This is an example of what kind of reproductive isolation?

Accepted Answer

The fact that the two species of frog mate during different times (early summer and late summer) indicates temporal separation, which is a type of pre-zygotic reproductive isolation. The other options are less likely to be applicable because they do not involve timing of reproductive behavior.

Question 5

A zookeeper is very upset because one of the lions jumped the fence of his enclosure and mated with a neighboring tigress. This mating produced a "liger." Which of the following statements is likely TRUE of this liger cub?

Accepted Answer

The answer of A zookeeper is very upset because one...

Question 6

A little girl notices that she has a male dog and a female cat in her house at the same time. The dog and cat are the same size, and they seem friendly enough. Why don't these two animals ever mate?

Accepted Answer

The reason why the dog and cat don't mate is behavioral isolation. Even though they are of similar size and seem friendly, they are two different species with different mating behaviors and instincts. Without those instincts, they won't mate. Additionally, dogs and cats have different courtship and mating behaviors, which would make it difficult for them to mate even if they wanted to. The other choices are not applicable as there is no temporal, ecological or geographic isolation present, and the animals are not different enough to be considered different species with different habitats.

Question 7

You observe two groups of frogs that are closely related. Males from each group "sing" with a species-specific song to attract a female frog. Females only respond to songs sung by males of their species. This is an example of _____ separation and _____-zygotic reproductive isolation between two species.

Accepted Answer

This is an example of behavioral isolation, as the frogs are separated by differences in their mating behaviors. It is also pre-zygotic, as the two species are unable to produce viable offspring due to differences in their mating behaviors before they have the opportunity to mate and produce a zygote.

Question 8

The reason that lions (which live in Africa) and tigers (which live in Asia) don't produce ligers (infertile offspring of lions and tigers) in the wild is likely the result of:

Accepted Answer

Lions and tigers do not naturally encounter each other in the wild due to their geographical separation, as lions are native to Africa and tigers to Asia, leading to ecological separation.

Question 9

Reproductive isolating mechanisms are divided into categories based on when they act. _____ isolating factors prevent fertilization from taking place; _____ isolating factors result in failure of the fertilized egg to develop into a fertile individual.

Accepted Answer

Pre-zygotic isolating factors prevent fertilization from taking place, while post-zygotic isolating factors result in failure of the fertilized egg to develop into a fertile individual.

Question 10

Imagine that a scientist wants to create a new species of minions-one that is a cross between a shark and a wolf. To his dismay, when he introduces shark sperm and wolf eggs into a petri dish, no viable embryos form. Why?

Accepted Answer

The correct answer is E because it addresses the fundamental biological barriers to cross-species reproduction. Pre-zygotic isolation mechanisms, such as incompatible reproductive proteins, and genetic incompatibility due to vast genomic differences between species like sharks and wolves, would prevent the formation of viable embryos.

Question 11

Recall the example of different ladybug species described in the text, which each feed on a different species of plant. If two such species inhabit the same types of plants but in different locations (i.e., one near the base of the plant and the other on the uppermost leaves), these species would be considered to be _____ separated.

Accepted Answer

The ladybug species are separated based on their ecological niches, i.e., the specific plant species they feed on and the location on the plant where they feed. This is an example of ecological separation. Temporal separation would imply that the ladybugs inhabit the same plant at different times, which is not the case in the example provided. Energetic separation refers to differences in the way organisms obtain energy and is not relevant to the ladybug example.

Question 12

Post-zygotic reproductive isolation may be due to temporal or ecological separation.

Accepted Answer

Post-zygotic reproductive isolation refers to mechanisms that occur after fertilization, preventing the development of viable or fertile offspring, and does not involve temporal or ecological separation, which are pre-zygotic mechanisms.

Question 13

You would expect similar species with a different number of chromosomes to be genetically compatible and therefore able to reproduce.

Accepted Answer

Different numbers of chromosomes can lead to infertility or sterility in hybrid offspring, and in some cases, can cause fatal genetic abnormalities. Therefore, species with different chromosome numbers are not always genetically compatible and may not be able to produce viable offspring.

Question 14

You observe two groups of freshwater fish that spawn at the same time of the year and in the same pond. After females lay their eggs on the pond bottom, males of both species attempt to fertilize them. After some investigation you realize that sperm from both species fertilize the eggs, but embryonic development stops shortly after fertilization when the eggs are fertilized by one species of males, but not by the other. This is an example of _____-zygotic reproductive isolation between the two species.

Accepted Answer

This is an example of post-zygotic reproductive isolation because fertilization occurs between the two species, but embryonic development stops shortly after.

Question 15

The longer two species have been separated, the greater the number of genetic differences between them.

Accepted Answer

This statement is true. Over time, genetic mutations accumulate and lead to differences between species that have been separated for longer periods of time.

Question 16

Which of the following represents genetic incompatibility?

Accepted Answer

Genetic incompatibility occurs when individuals from two different groups cannot produce fertile offspring due to differences in their genetic makeup. Choice D is the only option that describes this, as the two groups of snakes have a different number of chromosomes, which would prevent successful fertilization and reproduction. The other options describe other barriers to reproduction such as differences in diet, geography, and behavior, but not specifically genetic incompatibility.

Question 17

Examine Figure 22.10, below. Which of the following statements is the MOST accurate in reflecting levels of genetic divergence between different species of lice?  Photo sources: (left) Photo by Alex Popinga, courtesy of James Demastes; (right) Richard Ditch @ richditch.com.

Accepted Answer

According to the figure, G. cherriei and G. costaricensis share the most recent common ancestor and are thus expected to have accumulated the fewest genetic differences between them relative to the other Geomydoecus species. This is consistent with the pattern shown in the figure.

Question 18

You observe two groups of birds that appear to be closely related. Males from the first group have bright red stripes on their tail feathers that they display in a courtship dance preceding mating. Females only respond to coloring patterns exhibited by males of their species. This is an example of _____-zygotic reproductive isolation between two species.

Accepted Answer

This is an example of pre-zygotic reproductive isolation because the mechanism (bright red stripes on tail feathers used in courtship dances) prevents mating and fertilization between different species before the formation of a zygote.

Question 19

Which of the following statements reflects one way that two different species can produce hybrid offspring?

Accepted Answer

Hybrid offspring can occur between two species when they are closely enough related to produce offspring, but the genetic differences often result in those offspring being sterile, as seen in the case of mules, which are hybrids of horses and donkeys.

Question 20

Biochemical recognition systems within the stigma of a flowering plant prevent the pollen from a different species from developing a pollen tube and fertilizing its eggs. This is an example of what kind of reproductive isolation?

Accepted Answer

Biochemical recognition systems within the stigma of a flowering plant preventing the pollen from a different species from developing a pollen tube and fertilizing its eggs is an example of pre-zygotic isolation. It is specifically an example of lock and key, where the biochemical recognition systems act as a lock and the pollen must have a specific "key" (compatible molecules) to fertilize the egg.

Quiz 22: Species and Speciation

If two individuals from different species attempt to mate but fertilization fails to occur, this is likely the result of _ factors. However, if such a mating produces a zygote that fails to form a viable embryo, this is likely the result of _ factors.