Question 1

Certain proteins of the complex motor that drives bacterial flagella are modified versions of proteins that had previously belonged to plasma membrane pumps. This evidence supports the claim that

Accepted Answer

The fact that proteins from different structures (plasma membrane pumps) were re-purposed to form a complex structure (bacterial flagella motor) suggests that natural selection can produce new structures by building upon and modifying existing ones. This is consistent with the theory of evolution by natural selection.

Question 2

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 the Hox gene to be expressed along the tip of a vertebrate limb bud is an example of a change in a developmental gene or its regulation that altered the spatial organization of body parts. This change ultimately resulted in the evolution of the tetrapod limb.

Answer: D
 The term "heterochrony" describes a change in the timing or rate of developmental events, which can also result in altered spatial organization of body parts. However, this answer choice does not specifically address the genetic change related to the Hox gene that is mentioned in the question stem.

Answer options A, B, and E are incorrect because they do not accurately reflect the specific change described in the question stem. Choice A refers to an environmental influence on development, which is not relevant to this scenario. Choice B refers to retaining juvenile traits into adulthood, which is also not applicable in this context. Choice E refers to the process of gene duplication, which is not directly related to the Hox gene expression change outlined in the question.

Question 3

Which of the following steps has not yet been accomplished by scientists studying the origin of life?

Accepted Answer

Formation of protocells that use DNA to direct the polymerization of amino acids has not yet been accomplished by scientists studying the origin of life. While RNA has been found to play an important role in the early stages of life, the emergence of DNA as the primary hereditary molecule came later in evolution.

Question 4

The oxygen revolution changed Earth's environment dramatically. Which of the following took advantage of the presence of free oxygen in the oceans and atmosphere?

Accepted Answer

The presence of free oxygen in the oceans and atmosphere allowed for the evolution of cellular respiration, which used oxygen to help harvest energy from organic molecules. This metabolic process provided organisms with much more efficient energy production than anaerobic metabolism, and became a dominant form of energy production for many organisms.

Question 5

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 question states that in vertebrates, the rh gene family is responsible for the production of light-receptor pigments in the retina. While Pax-6 is involved in the production of light-receptor pigments, it is not responsible for the pigments in vertebrate eyes. The question also states that the rh gene is ancient and has been shown to cause the production of c-opsin in the marine ragworm, which helps regulate its biological clock. Therefore, it is more likely that during vertebrate evolution, the rh gene for biological clock opsin was co-opted as a gene for visual receptor pigments.

Question 6

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

Accepted Answer

Balancing organs in flies, known as halteres, were originally used as hindwings but got repurposed as modified organs to maintain balance during flight. This change in function represents an exaptation.

Question 7

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 a unique set of plant and animal species to evolve in isolation from nearby southeast Asia. This is known as biogeographical isolation and can result in speciation and distinct evolutionary paths. This is further supported by the fact that India is known for its high biodiversity and endemism, with many species found only on the Indian subcontinent. The other options (A, B, C, D) do not adequately explain the drastic differences in species between India and southeast Asia.

Question 8

A swim bladder is a gas-filled sac that helps fish maintain buoyancy. The evolution of the swim bladder from lungs of an ancestral fish is an example of

Accepted Answer

The swim bladder is believed to have evolved from the ancestral fish's lungs, which were originally used for breathing. This transformation is an example of exaptation, in which an existing structure takes on a new function over time.

Question 9

Fossilized stromatolites

Accepted Answer

Fossilized stromatolites resemble structures formed by bacterial communities that are found today in some warm, shallow, salty bays.

Question 10

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 Pax-6 produces different types of eyes in different organisms suggests that there are differences in the ways in which it is regulated, or controlled, during development. Other genes and environmental cues may interact with Pax-6 in different ways, resulting in the formation of compound eyes in flies, camera-type eyes in mammals, and other types of eyes in other organisms. Therefore, choice D is the best answer.

Question 11

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, both of which could lead to changes in body segment development and loss of flight wings.

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.
-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

The answer of The following questions refer to this hypothetical...

Question 13

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 above, which explanation is most likely?

Accepted Answer

The fact that all animals with eyes or eyespots studied so far share a gene in common, and that even the fruit fly Pax-6 can cause eye formation in eyeless fruit flies, suggests that Pax-6 was an innovation of an ancestral animal of the early Cambrian period. Animals with eyes or eyespots are likely descendants of this ancestor, which possessed the ability to form eyes due to the existence of Pax-6.

Question 14

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.
-Fly species W, found in a certain part of the island, produces fertile offspring with species Y. Species W does not produce fertile offspring with species X or Z. If no other species can hybridize, then species W and Y

Accepted Answer

Option A is correct because if species W and Y can produce fertile offspring, it means that their genomes are still similar enough for successful meiosis to occur in hybrid flies.
Option B is correct since species W and Y are descended from a common ancestor, and therefore, they have more genetic similarity to each other than with the other two species, which are not their direct descendants.
Option C is also correct because if the hybrids of species W and Y remain fertile over many generations and continue to interbreed, then the two species may gradually fuse into a single species. Therefore, it is a possibility.
Therefore, options A, B, and C are all correct, making choice D the correct answer.

Question 15

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 lead to the loss of genetic variation in a population, but it is not generally considered a direct factor in driving adaptive radiations. The other options - vacant ecological niches, colonization of a new region, evolutionary innovation, and exploitation of a food resource - can all contribute to adaptive radiations by providing opportunities for new species to diversify and occupy different roles in the ecosystem.

Quiz 25: The History of Life on Earth