Question 1

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

A)  The Pax-6 gene mutated to become the rh gene among early mammals. 
B)  During vertebrate evolution, the rh gene for biological clock opsin was co-opted as a gene for visual receptor pigments. 
C)  In animals more ancient than ragworms, the rh gene(s) coded for visual receptor pigments; in lineages more recent than ragworms, rh has flip-flopped several times between producing biological clock opsins and visual receptor pigments. 
D)  Pax-6 was lost from the mammalian genome, and replaced by the rh gene much later.

Question 2

The existence of evolutionary trends, such as increasing body sizes among horse species, is evidence that

Accepted Answer

A)  a larger volume-to-surface area ratio is beneficial to all mammals. 
B)  an unseen guiding force is at work. 
C)  evolution always tends toward increased complexity or increased size. 
D)  in particular environments, similar adaptations can be beneficial in more than one species. 
E)  evolution generally progresses toward some predetermined goal.

Question 3

The following questions refer to the description and figure below.
The figure 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 25.1
-How many other bands of sea-floor crust in Figure 25.1 have the same magnetic polarity as the crust that directly straddles the rift valley?

Accepted Answer

A)  two bands 
B)  four bands 
C)  six bands 
D)  eight bands 
E)  ten bands

Question 4

Figure 25.3
-Soon after the island of Hawaii rose above the sea surface (somewhat less than 1 million years ago), the evolution of life on this new island should have been most strongly influenced by

Accepted Answer

A)  genetic bottleneck. 
B)  sexual selection. 
C)  habitat differentiation. 
D)  founder effect.

Question 5

The snowball Earth hypothesis provides a possible explanation for the

Accepted Answer

A)  diversification of animals during the late Proterozoic era. 
B)  oxygenation of Earth's seas and atmosphere. 
C)  colonization of land by plants and fungi. 
D)  origin of oxygen-releasing photosynthesis. 
E)  existence of prokaryotes around hydrothermal vents on the ocean floor.

Question 6

Approximately how far back in time does the fossil record extend?

Accepted Answer

A)  3.5 million years 
B)  5.0 million years 
C)  3.5 billion years 
D)  5.0 billion years

Question 7

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

A)  duplicated all of the Hox genes in these flies' genomes. 
B)  altered the nucleotide sequence within a Hox gene. 
C)  altered the expression of a Hox gene. 
D)  all three of the above responses 
E)  two of the above answers are correct

Question 8

Recent evidence indicates that the first major diversification of multicellular eukaryotes may have coincided in time with the

Accepted Answer

A)  origin of prokaryotes. 
B)  switch to an oxidizing atmosphere. 
C)  melting that ended the "snowball Earth" period. 
D)  origin of multicellular organisms. 
E)  massive eruptions of deep-sea vents.

Question 9

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.
  
Figure 25.2
-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

A)  2, 4, 3, 1 
B)  2, 4, 1, 3 
C)  4, 2, 1, 3 
D)  4, 2, 3, 1

Question 10

The existence of the phenomenon of exaptation is most closely associated with which of the following observations that natural selection cannot fashion perfect organisms?

Accepted Answer

A)  Natural selection and sexual selection can work at cross-purposes to each other. 
B)  Evolution is limited by historical constraints. 
C)  Adaptations are often compromises. 
D)  Chance events affect the evolutionary history of populations in environments that can change unpredictably.

Question 11

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

A)  Pax-6 in all of these animals is not homologous; it arose independently in many different animal phyla due to intense selective pressure favoring vision. 
B)  The Pax-6 gene is really not "one" gene. It is many different genes that, over evolutionary time and due to convergence, have come to have a similar nucleotide sequence and function. 
C)  The Pax-6 gene was an innovation of an ancestral animal of the early Cambrian period. Animals with eyes or eyespots are descendants of this ancestor. 
D)  The perfectly designed Pax-6 gene appeared instantaneously in all animals created to have eyes or eyespots.

Question 12

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.
  
Figure 25.2
-In order to properly interpret sediment cores, it is necessary to apply the principle of

Accepted Answer

A)  catastrophism. 
B)  superposition. 
C)  punctuated equilibrium. 
D)  uniformitarianism. 
E)  gradualism.

Question 13

Which measurement(s)would help determine absolute dates by radiometric means?

Accepted Answer

A)  the accumulation of the daughter isotope 
B)  the loss of parent isotopes 
C)  the loss of daughter isotopes 
D)  Three of the responses above are correct. 
E)  Two of the responses above are correct.

Question 14

Which of the following is the most likely explanation for the modern-day distribution of dicynodont fossils?

Accepted Answer

A)  There had been two previous supercontinents that existed at different times long before the Permian period. 
B)  The dicynodonts were evenly distributed throughout all of Pangaea. 
C)  The dicynodonts were distributed more abundantly throughout Gondwanaland than throughout any other land mass. 
D)  The dicynodonts were amphibious and able to swim long distances. 
E)  The dicynodonts could survive for periods of months aboard "rafts" of vegetation, few of which made their way to the northern hemisphere.

Question 15

If two continents converge and are united, then the collision should cause

Accepted Answer

A)  a net loss of intertidal zone and coastal habitat. 
B)  the extinction of any species adapted to intertidal and coastal habitats. 
C)  an overall decrease in the surface area located in the continental interior. 
D)  a decrease in climatic extremes in the interior of the new supercontinent. 
E)  the maintenance of the previously existing ocean currents and wind patterns.

Question 16

Which event is nearest in time to the end of the period known as snowball Earth?

Accepted Answer

A)  oxygenation of Earth's seas and atmosphere 
B)  evolution of mitochondria 
C)  Cambrian explosion 
D)  evolution of true multicellularity 
E)  Permian extinction

Question 17

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

A)  the influence of environment on development. 
B)  paedomorphosis. 
C)  a change in a developmental gene or its regulation that altered the spatial organization of body parts. 
D)  heterochrony. 
E)  gene duplication.

Question 18

What is thought to be the correct sequence of these events, from earliest to most recent, in the evolution of life on Earth?
1)origin of mitochondria
2)origin of multicellular eukaryotes
3)origin of chloroplasts
4)origin of cyanobacteria
5)origin of fungal-plant symbioses

Accepted Answer

A)  4, 3, 2, 1, 5 
B)  4, 1, 2, 3, 5 
C)  4, 1, 3, 2, 5 
D)  4, 3, 1, 5, 2 
E)  4, 3, 1, 2, 5

Question 19

What is true of the Cambrian explosion?

Accepted Answer

A)  There are no fossils in geological strata that are older than the Cambrian explosion. 
B)  Only the fossils of microorganisms are found in geological strata older than the Cambrian explosion. 
C)  The Cambrian explosion is evidence for the instantaneous creation of life on Earth. 
D)  The Cambrian explosion marks the appearance of filter-feeding animals in the fossil record. 
E)  Recent evidence supports the contention that the Cambrian explosion may not have been as "explosive" as was once thought.

Question 20

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

Accepted Answer

A)  The species have become separated by convergent evolution. 
B)  The climates of the two regions are similar. 
C)  India is in the process of separating from the rest of Asia. 
D)  Life in India was wiped out by ancient volcanic eruptions. 
E)  India was a separate continent until 45 million years ago.

Exam 25: The History of Life on Earth