Question 1

Refer to the figure below illustrating the "RNA world" hypothesis.  Which statement about this hypothetical evolutionary model is true?
A) It supports the hypothesis that proteins appeared on Earth before nucleic acids.
B) It would be impossible in reality, since RNA is synthesized from DNA.
C) It would require prebiotic synthesis of fatty acids.
D) It is consistent with the activity of modern retroviruses that synthesize DNA.
E) It is inconsistent with the hypothesis that nucleic acids were the first catalysts.

Accepted Answer

The figure shows a possible evolutionary pathway in which RNA was the first genetic material and could catalyze its own replication as well as other reactions. This is consistent with the activity of modern retroviruses, which synthesize DNA from an RNA template. Option A is incorrect, as the RNA world hypothesis proposes the reverse: that nucleic acids appeared before proteins. Option B is incorrect, as RNA can self-replicate and does not require DNA for synthesis. Option C is not directly relevant to the RNA world hypothesis. Option E is also not correct, as the RNA world hypothesis proposes that nucleic acids were the first catalysts.

Question 2

Suppose that scientists succeed in creating experimental conditions that generate living cells from nonliving matter.Which statement best expresses how this achievement will affect thinking about the history of life on Earth?
A) The results will prove that life arose on Earth in a similar way, because it is so difficult to find just the right conditions to recreate the process in a lab.
B) The results will demonstrate that life could have arisen on Earth in a similar way, because we may never know what actual conditions were present on primitive Earth.
C) The results will suggest that life probably arose on Earth in a similar way, because scientists finally succeeded in reproducing the process in a lab.
D) The results will indicate that life could not have arisen on Earth in a similar way, because experiments in labs can never recreate exact conditions in the real world.
E) The results will indicate that life could not have arisen on Earth in a similar way, because there are too many variables and unknowns that make it impossible to test them all.

Accepted Answer

Even if scientists are successful in creating living cells from nonliving matter in a lab, it does not necessarily mean that the same conditions existed on primitive Earth. Therefore, the results will demonstrate that life could have arisen on Earth in a similar way, because we may never know what actual conditions were present on primitive Earth. This does not prove that life did arise in this way, but rather suggests that it is a possibility. Therefore, option B is the best choice. Options A, C, D, and E are mostly incorrect or irrelevant.

Question 3

Refer to the figure below showing the Miller‒Urey experiment. Research conducted later than the Miller‒Urey experiment showed that volcanic activity 4 billion years ago injected other gases, such as SO₂, into Earth's early environment.This information led to the conclusion that A) the original Miller-Urey experiment did not produce meaningful data. B) a modified experiment should be performed in which other gases would be added to the initial heated solution. C) the experiment required a longer running time to see whether the other gases would be produced. D) the beaker of condensed liquid and compounds should be heated in the presence of the additional gases. E) the Miller‒Urey experiment did not require modification, since cellular life existed earlier than 4 billion years ago.

Accepted Answer

The information about volcanic activity injecting other gases into Earth's early environment suggests that a modified Miller-Urey experiment should be performed in which those other gases are added to the initial heated solution. The original experiment only considered a limited range of gases, so adding in additional ones would produce a more accurate simulation of early Earth's conditions.

Question 4

Refer to the figure below showing a simplified time line of the origin of life.  Which event could have occurred before the evolution of RNA?
A) Formation of DNA
B) Evolution of cells
C) Prebiotic synthesis of amino acids
D) Development of ribozymes
E) Rise of protocells

Accepted Answer

The answer of Refer to the figure below showing a...

Question 5

Which was absent in the products analyzed at the conclusion of the Miller-Urey experiments?
A) Most of the amino acids used in protein synthesis
B) Small carbon sugars
C) Adenine and thymine
D) Nucleotides
E) Uracil

Accepted Answer

Nucleotides, the basic building blocks of nucleic acids like DNA and RNA, were not among the organic compounds produced in the Miller-Urey experiments. These experiments primarily yielded simple organic molecules such as amino acids, not the more complex molecules like nucleotides.

Question 6

RNA molecules that act as catalysts are called
A) ribozymes.
B) glycosidic linkages.
C) chaperonins.
D) disulfide bridges.
E) triglycerides.

Accepted Answer

RNA molecules that act as catalysts are called ribozymes.

Question 7

Retroviruses, such as HIV, have an enzyme that allows them to catalyze DNA synthesis from an RNA template.This evidence supports the hypothesis that
A) RNA itself cannot be a catalyst.
B) early life consisted of an "RNA world."
C) RNA probably came from an extraterrestrial source.
D) chemical evolution led to polymerization.
E) DNA polymers form from RNA monomers.

Accepted Answer

The fact that retroviruses can catalyze DNA synthesis from an RNA template suggests that RNA played a crucial role in early life, potentially as the first self-replicating molecule in an "RNA world." This hypothesis suggests that early life relied on RNA for both genetic information and catalytic function.

Question 8

Refer to the figure below showing the Miller‒Urey experiment. The experiment, which was performed in the 1950s, A) showed that Earth's early environment had an atmosphere of N₂, NH₃, CH₄, H₂O, and H₂. B) showed that Earth's early atmosphere consisted of a combination of gases that is different from the one that exists today. C) proved that carbon dioxide was present in Earth's early atmosphere. D) demonstrated prebiotic synthesis of small molecules of life. E) led to no meaningful conclusions, because there was no lightning in Earth's early environment.

Accepted Answer

The answer of Refer to the figure below showing the...

Question 9

Which was a limitation of the Miller-Urey experiments in the 1950s?
A) The experiments synthesized both d- and l-isomers of amino acids, but the amino acids in living things are always l-isomers.
B) The experimenters made assumptions about Earth's early atmosphere that were later found to be inaccurate.
C) DNA is not self-catalytic.
D) In living organisms today, peptide linkages are catalyzed by ribozymes.
E) The hot temperatures of the experiments denatured some of the proteins that were synthesized.

Accepted Answer

The Miller-Urey experiments assumed that Earth's early atmosphere was reducing, with little or no oxygen, which was later found to be inaccurate.

Question 10

Which of these substances, present in the prebiotic environment on Earth, could have been critical in making the chemical synthesis of biologically important polymers more favorable?
A) Water
B) Sodium ions
C) Methane
D) Nickel ions
E) Hydrogen

Accepted Answer

Nickel ions could have acted as catalysts in the prebiotic environment, facilitating the formation of complex organic molecules and polymers necessary for the origin of life.

Question 11

Which is evidence that supports the hypothesis that DNA could have evolved from RNA?
A) The discovery that retroviruses have an enzyme that catalyzes DNA synthesis from RNA
B) Evidence of the early emergence on Earth of chemical reactions that resulted in monomers
C) Evidence of the nearly spontaneous formation of lipid micelles on Earth
D) Evidence of the prebiotic chemical generation of cell-like compartments
E) The chemical traces of life found on meteorites

Accepted Answer

The discovery of retroviruses, which have an enzyme that can convert RNA into DNA, provides evidence that RNA could have evolved into DNA over time.

Answer: B
 The emergence of monomers on early Earth suggests that the building blocks of RNA and DNA were present and could have led to the evolution of DNA from RNA.

Answer: D
 The prebiotic generation of cell-like compartments provides evidence that early cells could have existed that could have evolved RNA into DNA over time.

Option C and E are not relevant to support the hypothesis that DNA could have evolved from RNA.

Question 12

Which statement is supported by the discovery that RNA can function as a catalyst?
A) Proteins were the first catalysts.
B) An "RNA world" of early life preceded the existence of DNA.
C) Prebiotic synthesis of the four bases of RNA is not necessary for life.
D) The prebiotic origin of small molecules was in ice on cold moons.
E) The prebiotic origin of small molecules occurred around hydrothermal vents.

Accepted Answer

The discovery that RNA can function as a catalyst supports the idea of an "RNA world" of early life preceding the existence of DNA, where RNA served both as an informational molecule and a catalyst. This hypothesis suggests that RNA was the first molecule to be able to perform both functions, which then paved the way for the evolution of proteins as catalysts.

Question 13

The "RNA world" hypothesis is supported by evidence that
A) RNA molecules spontaneously form spheres in water.
B) RNA can act as both genetic material and a catalyst.
C) amino acids can form RNA in particular chemical environments.
D) RNA can act as genetic material but not as a catalyst.
E) RNA monomers can form proteins.

Accepted Answer

The RNA world hypothesis proposes that RNA acted as genetic material and catalytic molecules before the evolution of DNA and proteins. This hypothesis is supported by evidence that RNA can act as both genetic material and a catalyst.

Question 14

Hot water containing iron and nickel emerges from below Earth's crust at deep ocean hydrothermal vents where there is no oxygen.These metals catalyze the polymerization of amino acids in the absence of oxygen.This evidence supports the hypothesis of
A) the prebiotic synthesis of large molecules in Earth's early environment.
B) photosynthesis by cyanobacteria 3.5 billion years ago.
C) the prebiotic synthesis of small molecules in the ice of Europa, a moon of Jupiter.
D) the evolution of whales.
E) an extraterrestrial origin of life.

Accepted Answer

The presence of iron and nickel catalyzing the polymerization of amino acids in the absence of oxygen supports the hypothesis of prebiotic synthesis of large molecules in Earth's early environment. This is because it suggests that the conditions on early Earth were conducive to the formation of complex organic molecules, which may have eventually led to life. The other options are not supported by this evidence.

Question 15

Chemical reaction rates vary depending on the concentrations of reactants.In which primitive Earth environment would conditions have shifted reactant concentrations to favor increased polymerization of monomers?
A) Rocky outcroppings with full sun exposure
B) Deep, wide freshwater lakes
C) Hot, sandy beaches
D) Shallow ponds with clay bottoms
E) Thermal vents deep in a salty ocean

Accepted Answer

Shallow ponds with clay bottoms would provide a confined space with limited water flow, favoring the accumulation of monomers. Clay particles have a negative charge that may concentrate and bind positively charged monomers, increasing their local concentration and thus the likelihood of polymerization.

Question 16

Whether the process is abiotic or occurs in an organism, the synthesis of macromolecules
A) occurs with an increase of entropy.
B) is spontaneous.
C) requires energy.
D) results in a more random system.
E) gives off heat.

Accepted Answer

The synthesis of macromolecules requires energy, which is in contrast to spontaneous processes that occur without the input of energy. This process results in a decrease in entropy, as macromolecules are more ordered than their individual monomers. Therefore, options A, B, D, and E are incorrect.

Question 17

Which may have facilitated the polymerization of the large molecules of life on primitive Earth?
A) Ice crystals
B) Evaporation in hot pools at the edges of oceans
C) Ribozymes
D) Early proteins
E) Lightning strikes in an anaerobic environment of methane, ammonia, hydrogen, and water vapor.

Accepted Answer

Evaporation in hot pools at the edges of oceans could have concentrated organic molecules, facilitating their polymerization into larger molecules.

Question 18

What evidence supports the possibility that life may have come from outside of Earth?
A) Amino acids in a meteorite were found to be a mixture of l- and d-isomers.
B) DNA molecules have been found in meteorites.
C) Other bodies in the solar system have, or once had, oxygen.
D) Other bodies in the solar system have, or once had, long-chain polypeptide molecules.
E) Other bodies in the solar system have gaseous atmospheres.

Accepted Answer

Amino acids found in meteorites, which are a mixture of l- and d-isomers, suggest that some of the basic building blocks of life could have originated from space. This supports the panspermia hypothesis, which proposes that life, or the precursors of life, came to Earth from outer space.

Question 19

In 1969, scientists shaved off pieces of the Murchison meteorite and found both D- and L-isomers of ten amino acids.Only L-isomers of amino acids are made by living organisms on Earth.This indicates that
A) Earth's amino acids could not have had an extraterrestrial origin.
B) the meteorite's amino acids as a whole could not have resulted from contamination by Earth organisms.
C) basic chemical building blocks of life have only formed on Earth.
D) life must have originated somewhere other than Earth.
E) life arose in many places besides Earth.

Accepted Answer

The presence of both D- and L-isomers of amino acids in the Murchison meteorite, including the L-isomers only produced by living organisms on Earth, suggests that the meteorite's amino acids did not come from contamination by Earth organisms. Therefore, option B is the best choice. The presence of extraterrestrial amino acids indicates that basic chemical building blocks of life can form elsewhere in the universe, and that life may have originated in many places besides Earth, making options C, D, and E less likely. Option A is also less likely because the extraterrestrial origin of amino acids is supported by the evidence.

Question 20

The Miller-Urey experiments demonstrated that A) under specific conditions, the basic building blocks of life can form. B) life on Earth came from other bodies in the solar system. C) CO₂, N₂, H₂S, and SO₂ were probably present in Earth's early atmosphere. D) volcanic eruptions may have released CO₂, N₂, H₂S, and SO₂ into Earth's early atmosphere. E) ice is present in meteorites and on Mars.

Accepted Answer

The Miller-Urey experiments were designed to simulate the conditions of early Earth's atmosphere and demonstrated that under these conditions, amino acids and other organic compounds essential for life could form. Therefore, choice A is the correct answer. Choices B, C, D, and E are not supported by the Miller-Urey experiments.

Quiz 4: Nucleic Acids and the Origin of Life

Refer to the figure below illustrating the "RNA world" hypothesis. Which statement about this hypothetical evolutionary model is true?

Suppose that scientists succeed in creating experimental conditions that generate living cells from nonliving matter.Which statement best expresses how this achievement will affect thinking about the history of life on Earth?

Refer to the figure below showing the Miller‒Urey experiment. Research conducted later than the Miller‒Urey experiment showed that volcanic activity 4 billion years ago injected other gases, such as SO2, into Earth's early environment.This information led to the conclusion that

Refer to the figure below showing a simplified time line of the origin of life. Which event could have occurred before the evolution of RNA?

Which was absent in the products analyzed at the conclusion of the Miller-Urey experiments?

RNA molecules that act as catalysts are called

Retroviruses, such as HIV, have an enzyme that allows them to catalyze DNA synthesis from an RNA template.This evidence supports the hypothesis that

Refer to the figure below showing the Miller‒Urey experiment. The experiment, which was performed in the 1950s,

Which was a limitation of the Miller-Urey experiments in the 1950s?

Which of these substances, present in the prebiotic environment on Earth, could have been critical in making the chemical synthesis of biologically important polymers more favorable?

Which is evidence that supports the hypothesis that DNA could have evolved from RNA?

Which statement is supported by the discovery that RNA can function as a catalyst?

The "RNA world" hypothesis is supported by evidence that

Hot water containing iron and nickel emerges from below Earth's crust at deep ocean hydrothermal vents where there is no oxygen.These metals catalyze the polymerization of amino acids in the absence of oxygen.This evidence supports the hypothesis of

Chemical reaction rates vary depending on the concentrations of reactants.In which primitive Earth environment would conditions have shifted reactant concentrations to favor increased polymerization of monomers?

Whether the process is abiotic or occurs in an organism, the synthesis of macromolecules

Which may have facilitated the polymerization of the large molecules of life on primitive Earth?

What evidence supports the possibility that life may have come from outside of Earth?

In 1969, scientists shaved off pieces of the Murchison meteorite and found both D- and L-isomers of ten amino acids.Only L-isomers of amino acids are made by living organisms on Earth.This indicates that

The Miller-Urey experiments demonstrated that

Refer to the figure below showing the Miller‒Urey experiment. Research conducted later than the Miller‒Urey experiment showed that volcanic activity 4 billion years ago injected other gases, such as SO₂, into Earth's early environment.This information led to the conclusion that