Question 1

An organism has a relatively large number of Hox genes in its genome. Which of the following is true of this organism?

Accepted Answer

A) These genes are fundamental, and are expressed in all cells of the organism. 
B) The organism must have multiple paired appendages along the length of its body. 
C) The organism has the genetic potential to have a relatively complex anatomy. 
D) Most of its Hox genes owe their existence to gene fusion events. 
E) Its Hox genes cooperate to bring about sexual maturity at the proper stage of development.

Question 2

The first genes on Earth were probably

Accepted Answer

A) DNA produced by reverse transcriptase from abiotically produced RNA. 
B) DNA molecules whose information was transcribed to RNA and later translated in polypeptides. 
C) auto-catalytic RNA molecules. 
D) oligopeptides located within protobionts.

Question 3

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

A) adaptive radiation. 
B) species selection. 
C) sexual selection. 
D) allometric growth. 
E) habitat differentiation.

Question 4

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 5

The major evolutionary episode corresponding most closely in time with the formation of Pangaea was the

Accepted Answer

A) Cambrian explosion. 
B) Permian extinctions. 
C) Pleistocene ice ages. 
D) Cretaceous extinctions.

Question 6

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.
 
-In order to assign absolute dates to fossils in this sediment core, it would be most helpful if

Accepted Answer

A) we knew the order in which the fossils occurred in the core. 
B) the sediments had not been affected by underwater currents during their deposition. 
C) volcanic ash layers were regularly interspersed between the sedimentary strata. 
D) metamorphic rock strata alternated with sedimentary rock strata. 
E) fossils throughout the column had equal ratios of a parental radioisotope to its daughter isotope.

Question 7

Larval flies (maggots)express the Ubx gene in all of their segments, and thereby lack appendages. If this same gene continued to be expressed throughout subsequent developmental stages, except in the head region, and if the result was a fit, sexually mature organism that still strongly resembled a maggot, this would be an example of

Accepted Answer

A) paedomorphosis. 
B) homochrony. 
C) heterochrony. 
D) Two of the responses above are correct.

Question 8

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

A) the evolution of cellular respiration, which used oxygen to help harvest energy from organic molecules 
B) the persistence of some animal groups in anaerobic habitats 
C) the evolution of photosynthetic pigments that protected early algae from the corrosive effects of oxygen 
D) the evolution of chloroplasts after early protists incorporated photosynthetic cyanobacteria 
E) the evolution of multicellular eukaryotic colonies from communities of prokaryotes

Question 9

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

Accepted Answer

A) synthesis of small RNA polymers by ribozymes 
B) abiotic synthesis of polypeptides 
C) formation of molecular aggregates with selectively permeable membranes 
D) formation of protocells that use DNA to direct the polymerization of amino acids 
E) abiotic synthesis of organic molecules

Question 10

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 11

Several scientific laboratories across the globe are involved in research concerning the origin of life on Earth. Which of these questions is currently the most problematic and would have the greatest impact on our understanding if we were able to answer it?

Accepted Answer

A) How can amino acids, simple sugars, and nucleotides be synthesized abiotically? 
B) How can RNA molecules catalyze reactions? 
C) How did RNA sequences come to carry the code for amino acid sequences? 
D) How could polymers involving lipids and/or proteins form membranes in aqueous environments? 
E) How can RNA molecules act as templates for the synthesis of complementary RNA molecules?

Question 12

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 13

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 labelled "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.
 
-How many other bands of sea-floor crust in the figure 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 14

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 labelled "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.
 
-If a particular marine organism is fossilized in the sediments immediately overlying the igneous rock at the arrow labeled "II," at which other location, labeled A-E, would a search be most likely to find more fossils of this organism?

Accepted Answer

A) B only 
B) C only 
C) D only 
D) B and C 
E) C and D

Question 15

Bagworm moth caterpillars feed on evergreens and carry a silken case or bag around with them in which they eventually pupate. Adult female bagworm moths are larval in appearance; they lack the wings and other structures of the adult male and instead retain the appearance of a caterpillar even though they are sexually mature and can lay eggs within the bag. This is a good example of

Accepted Answer

A) allometric growth. 
B) paedomorphosis. 
C) sympatric speciation. 
D) adaptive radiation. 
E) changes in homeotic genes.

Question 16

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.
 
-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 17

The synthesis of new DNA requires the prior existence of oligonucleotides to serve as primers. On Earth, these primers are small RNA molecules. This latter observation is evidence in support of the hypothesized existence of

Accepted Answer

A) a snowball Earth. 
B) earlier genetic systems than those based on DNA. 
C) the abiotic synthesis of organic monomers. 
D) the delivery of organic matter to Earth by meteors and comets. 
E) the endosymbiotic origin of mitochondria and chloroplasts.

Question 18

Evolution includes all of the following points with the exception of

Accepted Answer

A) species can undergo species selection just like populations of individuals undergo natural selection. 
B) differential speciation success in macroevolution plays a similar role to differential reproductive success in microevolution. 
C) evolutionary trends result from natural selection. 
D) complex biological structures can evolve through incremental modifications, which benefit the organisms that possess them. 
E) some evolutionary trends are goal oriented.

Question 19

What is true of the fossil record of mammalian origins?

Accepted Answer

A) It is a good example of punctuated equilibrium. 
B) It shows that mammals and birds evolved from the same kind of dinosaur. 
C) It includes transitional forms with progressively specialized teeth. 
D) It indicates that mammals and dinosaurs did not overlap in geologic time. 
E) It includes a series that shows the gradual change of scales into fur.

Question 20

Which of the following statements does not apply to Hox genes?

Accepted Answer

A) They are a type of homeotic gene. 
B) They alter the timing of reproductive development. 
C) They provide positional information in animal embryos. 
D) Changes in how two Hox genes in snakes are expressed results in suppression of limb formation.

Exam 25: The History of Life on Earth