Question 1

The following questions refer to the description below.
All animals with eyes or eyespots that have been studied so far share a gene in common. When mutated, the gene Pax-6 causes lack of eyes in fruit flies, tiny eyes in mice, and missing irises (and other eye parts) in humans. The sequence of Pax-6 in humans and mice is identical. There are so few sequence differences with fruit fly Pax-6 that the human/mouse version can cause eye formation in eyeless fruit flies, even though vertebrates and invertebrates last shared a common ancestor more than 500 million years ago.
-Pax-6 usually causes the production of a type of light-receptor pigment. In vertebrate eyes, though, a different gene (the rh gene family) is responsible for the light-receptor pigments of the retina. The rh gene, like Pax-6, is ancient. In the marine ragworm, for example, the rh gene causes production of c-opsin, which helps regulate the worm's biological clock. Which of these most likely accounts for vertebrate vision?

Accepted Answer

The passage states that "In vertebrate eyes, though, a different gene (the rh gene family) is responsible for the light-receptor pigments of the retina" and suggests that during vertebrate evolution, the rh gene for biological clock opsin was co-opted as a gene for visual receptor pigments. There is no evidence in the passage to support any of the other answer choices.

Question 2

Adaptive radiations can be a direct consequence of four of the following five factors. Select the exception.

Accepted Answer

Genetic drift is a random process that can cause changes in the frequency of alleles in a population over time, but it is not a direct factor that leads to an adaptive radiation. The other factors listed (vacant ecological niches, colonization of an isolated region with suitable habitat and few competitors, evolutionary innovation, and an adaptive radiation in a food source) are all direct factors that can lead to adaptive radiations.

Question 3

Figure 23.3
-Hawaii is the most southeastern of the seven islands and is also closest to the sea-floor spreading center from which the Pacific plate originates, which lies about 5,600 km further to the southeast. Assuming equal sedimentation rates, what should be the location of the thickest sediment layer and, thus, the area with the greatest diversity of fossils above the oceanic crust?

Accepted Answer

The thickest sediment layer and thus the area with the greatest diversity of fossils above the oceanic crust would be around the base of Kauai, the oldest of the Hawaiian islands. This is because over time, sediment accumulates on the ocean floor, and older areas like around Kauai would have had more time for sediment to accumulate compared to newer areas like Hawaii.

Question 4

The following questions refer to the description below.
All animals with eyes or eyespots that have been studied so far share a gene in common. When mutated, the gene Pax-6 causes lack of eyes in fruit flies, tiny eyes in mice, and missing irises (and other eye parts) in humans. The sequence of Pax-6 in humans and mice is identical. There are so few sequence differences with fruit fly Pax-6 that the human/mouse version can cause eye formation in eyeless fruit flies, even though vertebrates and invertebrates last shared a common ancestor more than 500 million years ago.
-The appearance of Pax-6 in all animals with eyes can be explained in multiple ways. Based on the information, which explanation is most likely?

Accepted Answer

The description states that the Pax-6 gene was an innovation of an ancestral animal of the early Cambrian period and that animals with eyes or eyespots are descendants of this ancestor. This is the most likely explanation given the information provided.

Question 5

A genetic change that caused a certain Hox gene to be expressed along the tip of a vertebrate limb bud instead of farther back helped make possible the evolution of the tetrapod limb. This type of change is illustrative of

Accepted Answer

The genetic change that caused a Hox gene to be expressed differently is an example of a change in a developmental gene or its regulation, which altered the spatial organization of body parts. This is known as a cis-regulatory change and can lead to the evolution of novel features or structures in organisms.

Answer: D
 Heterochrony refers to changes in the timing of developmental events, such as the rate of growth or the onset of maturation. While this type of change can also contribute to the evolution of new features, it is not the most relevant concept for this particular example, in which a change in Hox gene expression altered the spatial organization of body parts.

Answer: A, B, E
 None of these choices accurately describes the genetic change that helped make the tetrapod limb possible. Environmental influences on development, paedomorphosis, and gene duplication can all be important factors in evolution, but they are not specifically relevant to this example.

Question 6

A swim bladder is a gas-filled sac that helps fish maintain buoyancy. The evolution of the swim bladder from the air-breathing organ (a simple lung) of an ancestral fish is an example of

Accepted Answer

The swim bladder evolved from the air-breathing organ of an ancestral fish through exaptation, which is the evolution of a structure for one function that is later co-opted for another function. In this case, the gas-filled sac that originally helped fish breathe air was later adapted for use as a buoyancy organ. The swim bladder is not an evolutionary trend, as it is not a shared characteristic that has evolved in a linear fashion across multiple species. Changes in Hox gene expression and paedomorphosis are not directly relevant to the evolution of the swim bladder. Adaptive radiation may be relevant if multiple species evolved different swim bladder structures in response to different ecological niches, but the question only refers to the evolution of the swim bladder in general.

Question 7

The following questions refer to the description below.
All animals with eyes or eyespots that have been studied so far share a gene in common. When mutated, the gene Pax-6 causes lack of eyes in fruit flies, tiny eyes in mice, and missing irises (and other eye parts) in humans. The sequence of Pax-6 in humans and mice is identical. There are so few sequence differences with fruit fly Pax-6 that the human/mouse version can cause eye formation in eyeless fruit flies, even though vertebrates and invertebrates last shared a common ancestor more than 500 million years ago.
-Fruit fly eyes are of the compound type, which is structurally very different from the camera-type eyes of mammals. Even the camera-type eyes of molluscs, such as octopi, are structurally quite different from those of mammals. Yet, fruit flies, octopi, and mammals possess very similar versions of Pax-6. The fact that the same gene helps produce very different types of eyes is most likely due to

Accepted Answer

The fact that different organisms with different types of eyes all have similar versions of Pax-6 suggests that the gene is involved in the formation of eyes in general, rather than the specific structure of any particular type of eye. The variations in eye structure among different organisms are likely due to differences in the control of Pax-6 expression, rather than variations in the nucleotide sequence or number of Pax-6 genes.

Question 8

The following questions refer to the description and Figure 23.1.
Figure 23.1 represents a cross section of the sea floor through a mid-ocean rift valley, with alternating patches of black and white indicating sea floor with reversed magnetic polarities. At the arrow labeled "I" (the rift valley), the igneous rock of the sea floor is so young that it can be accurately dated using carbon-14 dating. At the arrow labeled "III," however, the igneous rock is about 1 million years old, and potassium-40 dating is typically used to date such rocks. Note: The horizontal arrows indicate the direction of sea-floor spreading, away from the rift valley.
  Figure 23.1
-How many other bands of sea-floor crust in Figure 23.1 have the same magnetic polarity as the crust that directly straddles the rift valley?

Accepted Answer

The crust that directly straddles the rift valley has normal polarity. The four bands on either side of the rift valley also have normal polarity.

Question 9

The following questions refer to the description and Figure 23.1.
Figure 23.1 represents a cross section of the sea floor through a mid-ocean rift valley, with alternating patches of black and white indicating sea floor with reversed magnetic polarities. At the arrow labeled "I" (the rift valley), the igneous rock of the sea floor is so young that it can be accurately dated using carbon-14 dating. At the arrow labeled "III," however, the igneous rock is about 1 million years old, and potassium-40 dating is typically used to date such rocks. Note: The horizontal arrows indicate the direction of sea-floor spreading, away from the rift valley.
  Figure 23.1
-If a particular marine organism is fossilized in the sediments immediately overlying the igneous rock at the arrow labeled "II," at which other location(s), labeled A-E, would a search be most likely to find more fossils of this organism?

Accepted Answer

The answer of The following questions refer to the description...

Question 10

Which of these fly organs, as they exist in current fly populations, best fits the description of an exaptation?

Accepted Answer

Balancing organs in modern flies, known as halteres, have evolved from hindwings which are no longer used for flight. Therefore, they are considered an exaptation - a structure that has evolved for one purpose but then become co-opted for another purpose.

Question 11

A researcher discovers a fossil of what appears to be one of the oldest-known multicellular organisms. The researcher could estimate the age of this fossil based on

Accepted Answer

The most accurate way to estimate the age of a fossil is through radiometric dating. Carbon-14 dating is only effective for fossils up to 50,000 years old, while the age of the oldest-known multicellular organisms is much older than that. Carbon-14 dating is also not as reliable for sedimentary rocks. Uranium-238 dating is reliable for rocks and fossils that are millions of years old. Uranium-238 is commonly found in volcanic layers surrounding sedimentary rocks, making it the best choice for dating the oldest-known multicellular organisms.

Question 12

The following questions refer to this hypothetical situation.
A female fly, full of fertilized eggs, is swept by high winds to an island far out to sea. She is the first fly to arrive on this island, and the only fly to arrive in this way. Thousands of years later, her numerous offspring occupy the island, but none of them resembles her. There are, instead, several species, each of which eats only a certain type of food. None of the species can fly, for their flight wings are absent, and their balancing organs (in other words, halteres) are now used in courtship displays. The male members of each species bear modified halteres that are unique in appearance to their species. Females bear vestigial halteres. The ranges of all of the daughter species overlap.
-In each fly species, the entire body segment that gave rise to the original flight wings is missing. The mutation(s) that led to the flightless condition could have

Accepted Answer

The mutation(s) could have altered the nucleotide sequence within a Hox gene or altered the expression of a Hox gene, affecting the development of wings and halteres.

Question 13

Which factor most likely caused animals and plants in India to differ greatly from species in nearby Southeast Asia?

Accepted Answer

India was a separate continent until 45 million years ago, which allowed for distinct evolution of species that were isolated from the rest of Asia.

Question 14

Figure 23.2
The following questions refer to the paragraph below.
A sediment core is removed from the floor of an inland sea. The sea has been in existence, off and on, throughout the entire time that terrestrial life has existed. Researchers wish to locate and study the terrestrial organisms fossilized in this core. The core is illustrated as a vertical column, with the top of the column representing the most recent strata and the bottom representing the time when land was first colonized by life.
-Assuming the existence of fossilized markers for each of the following chemicals, what is the sequence in which they should be found in this sediment core, working from ancient sediments to recent sediments? 1. chitin coupled with protein
2) chlorophyll
3) bone
4) cellulose

Accepted Answer

The answer of  Figure 23.2
The following questions refer to...

Question 15

Upon being formed, oceanic islands, such as the Hawaiian Islands, should feature what characteristic, leading to which phenomenon?

Accepted Answer

Oceanic islands are isolated and have limited resources, which allows for a variety of empty ecological niches. This leads to adaptive radiation, where different species adapt to fill those niches and evolve into new species. This is seen in the Hawaiian Islands, where a single ancestral plant species has diversified into hundreds of different species due to the varied ecological niches available.

Question 16

If these fly species lost the ability to fly independently of each other as a result of separate mutation events in each lineage, then the flightless condition in these species could be an example of

Accepted Answer

This is an example of species selection, where similar evolutionary pressures result in the loss of a trait (in this case, flight) in different lineages. This is different from adaptive radiation, which involves the diversification of species into different ecological niches, and sexual selection, which involves selection for traits that increase mating success. Allometric growth and habitat differentiation are also unrelated to the loss of flight in these fly species.

Question 17

The following questions refer to the description and Figure 23.1.
Figure 23.1 represents a cross section of the sea floor through a mid-ocean rift valley, with alternating patches of black and white indicating sea floor with reversed magnetic polarities. At the arrow labeled "I" (the rift valley), the igneous rock of the sea floor is so young that it can be accurately dated using carbon-14 dating. At the arrow labeled "III," however, the igneous rock is about 1 million years old, and potassium-40 dating is typically used to date such rocks. Note: The horizontal arrows indicate the direction of sea-floor spreading, away from the rift valley.
  Figure 23.1
-Assuming that the rate of sea-floor spreading was constant during the 1-million-year period depicted in Figure 23.1, what should be the approximate age of marine fossils found in undisturbed sedimentary rock immediately overlying the igneous rock at the arrow labeled "II"?

Accepted Answer

Because the age of the igneous rock at the arrow labeled "II" is approximately halfway between the age that can be accurately dated using carbon-14 dating (arrow I) and the age that typically requires potassium-40 dating (arrow III), it is estimated to be around 500,000 years old. Therefore, marine fossils found in undisturbed sedimentary rock immediately overlying the igneous rock at the arrow labeled "II" should also be approximately 500,000 years old.

Question 18

Figure 23.3
-According to the theory of sea-floor spreading, oceanic islands, such as the Hawaiian Islands depicted in Figure 23.3, form as oceanic crustal plates move over a stationary "hot spot" in the mantle. Currently, the big island of Hawaii is thought to be over a hot spot, which is why it is the only one of the seven islands that has active volcanoes. What should be true of the island of Hawaii? 1. Scientists in search of ongoing speciation events are more likely to find them here than on the other six islands.
2) Its species should be more closely related to those of nearer islands than to those of farther islands.
3) It should have a rich fossil record of terrestrial organisms.
4) There is a good chance of finding endemic species on this island.
5) On average, it should have fewer species per unit surface area than the other six islands.

Accepted Answer

The presence of an active volcanism, combined with isolation from other land masses, provides a unique opportunity for ongoing speciation events on the island. The island's species should have closer similarities to those on neighboring islands due to the proximity and potential for gene flow. The isolation and unique geologic history make it likely to find endemic species on the island. Additionally, the island's smaller size and younger geological age suggest that it may have fewer species per unit surface area compared to the larger, older islands. However, there is no reason to expect a rich fossil record of terrestrial organisms.

Quiz 23: Broad Patterns of Evolution