Question 1

What is true of the fossil record of mammalian origins?

Accepted Answer

The fossil record of mammalian origins includes transitional forms with progressively specialized teeth, indicating gradual evolution towards modern mammalian dental patterns. This is one of the key pieces of evidence in support of evolutionary theory. Options A, B, D, and E are false.

Question 2

An early consequence of the release of oxygen gas by plant and bacterial photosynthesis was to

Accepted Answer

Oxygen is a highly reactive molecule and would have immediately reacted with iron in ocean water and terrestrial rocks to form iron oxides, known as rust. This is evident in iron-rich rocks that are millions of years old, which show signs of having been exposed to oxygen.

Question 3

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

Understanding how RNA sequences came to carry the code for amino acid sequences would provide insight into the first steps of protein synthesis and the emergence of life. It would also provide information on how genetic information was transferred and replicated.

Question 4

What evidence strongly suggests that RNA instead of DNA was the first genetic material?

Accepted Answer

RNA was likely the first genetic material because it is capable of both self-replication and carrying out catalytic functions, while DNA lacks the ability to carry out catalytic functions. This suggests that RNA was able to perform both tasks when the first genetic material was evolving, whereas DNA only evolved to carry genetic information later on. Additionally, RNA is simpler in structure than DNA, which could make it more likely to have arisen first. The fragility of DNA and the lack of necessary nucleotide components are not as strong pieces of evidence as the unique properties of RNA.

Question 5

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

Accepted Answer

The fossil record extends back approximately 3.5 billion years, which is the age of the oldest known stromatolite fossils. Fossils from organisms with hard shells, bones, or other body parts can be found in rocks that are a few hundred million years old, while more recent fossils can be found in rocks that are only a few thousand years old.

Question 6

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

Accepted Answer

The answer of Which measurement(s)would help determine absolute dates by...

Question 7

The first genes on Earth were probably

Accepted Answer

The RNA world hypothesis suggests that the first self-replicating entities on Earth were RNA molecules. It is believed that these RNA molecules possessed the ability to not only store genetic information, but also catalyze chemical reactions necessary for their own replication, making them auto-catalytic. This would have eventually led to the production of DNA through reverse transcription. Option A is incorrect because DNA was not present in the initial stages of life on Earth. Option B is also incorrect because it suggests that DNA preceded RNA, which is not supported by current scientific evidence. Option D is incorrect because oligopeptides are not capable of self-replication and would not be considered the first genes.

Question 8

Which of the following factors weaken(s)the hypothesis of abiotic synthesis of organic monomers in early Earth's atmosphere?
1)the relatively short time between intense meteor bombardment and the appearance of the first life-forms
2)the lack of experimental evidence that organic monomers can form by abiotic synthesis
3)uncertainty about which gases comprised early Earth's atmosphere

Accepted Answer

The answer of Which of the following factors weaken(s)the hypothesis...

Question 9

If natural selection in a particular environment favored genetic systems that permitted the production of daughter "cells" that were genetically dissimilar from the mother "cells," then one should expect selection for which of the following?
I.polynucleotide polymerase with low mismatch error rates
II.polynucleotide polymerases without proofreading capability
III.batteries of efficient polynucleotide repair enzymes
IV.polynucleotide polymerases with proofreading capability
V.polynucleotide polymerases with high mismatch error rates

Accepted Answer

If natural selection favored genetic systems that produced daughter cells genetically dissimilar from the mother cells, it would select for mechanisms that increase genetic variability. Polynucleotide polymerases without proofreading capability (II) and those with high mismatch error rates (V) would increase the likelihood of mutations, thereby increasing genetic diversity among offspring.

Question 10

What is true of the amino acids that might have been delivered to Earth within carbonaceous chondrites?

Accepted Answer

Carbonaceous chondrites have been found to contain a wider variety of amino acids than those that are used by living organisms on Earth today, indicating a rich chemical diversity in these space rocks.

Question 11

If the half-life of carbon-14 is about 5730 years,then a fossil that has one-sixteenth the normal proportion of carbon-14 to carbon-12 should be about how many years old?

Accepted Answer

The fossil has 1/16 the normal proportion of carbon-14, which means it has gone through 4 half-lives (since 2^4 = 16). Multiplying the half-life of carbon-14 (5,730 years) by 4 gives 22,920 years, which rounds to option E, 22,900 years.

Question 12

What is true of the Cambrian explosion?

Accepted Answer

Recent evidence suggests that the Cambrian explosion may not have been as rapid as previously thought, as some ancestral forms may have existed before the explosion, and some Cambrian organisms may have originated from earlier, Ediacaran fauna. Option A is false, as there are fossils found in strata older than the Cambrian, and option B is false as there are fossils of larger animals in older strata. Option C is false from a scientific standpoint, as it suggests creationism. Option D is partly true but doesn't encompass the broader view of the Cambrian explosion.

Question 13

Which of the following is a defining characteristic that all protocells had in common?

Accepted Answer

The surrounding membrane or membrane-like structure is a defining characteristic that all protocells had in common, as it allowed for separation from the environment and regulation of internal conditions. The other characteristics listed are not universally present in all protocells.

Question 14

If a fossil is encased in a stratum of sedimentary rock without any strata of igneous rock (for example,lava,volcanic ash)nearby,then it should be

Accepted Answer

Sedimentary rocks are formed from the accumulation of sediments, which can come from various sources and times, making it difficult to date them precisely using radiometric dating. This method works best with igneous rocks, which form from the cooling of magma or lava and can be dated by measuring the decay of radioactive isotopes present at the time of the rock's formation.

Question 15

Which organisms would you expect to be most poorly represented in the fossil record?

Accepted Answer

The answer of Which organisms would you expect to be...

Question 16

Which of the following is the correct sequence of events in the origin of life?
I.formation of protobionts
II.synthesis of organic monomers
III.synthesis of organic polymers
IV.formation of DNA-based genetic systems

Accepted Answer

The synthesis of organic monomers (II) had to occur before the synthesis of organic polymers (III) since monomers are the building blocks of polymers. Once polymers were formed, the next step was the formation of protobionts (I) which were structures that had some properties of living cells, such as a membrane-like boundary, but were not yet capable of reproduction or other functions of true cells. Finally, the formation of DNA-based genetic systems (IV) allowed for true genetic information to be passed on and evolve, marking the beginning of life as we know it.

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

The statement about small RNA molecules serving as primers for DNA synthesis suggests that there was a genetic system based on RNA before DNA. This supports the idea of earlier genetic systems than those based on DNA.

Question 18

Which of the following statements provides the strongest evidence that prokaryotes evolved before eukaryotes?

Accepted Answer

The oldest fossilized cells resemble prokaryotes, indicating that these simple cells existed before the more complex eukaryotic cells evolved. This is stronger evidence than options A, C, and D, which do not necessarily address the timeline of evolution, and option B, which suggests that prokaryotes were present on ancient meteorites but does not provide direct evidence of their evolutionary history.

Question 19

Which listing of geological periods is in the correct order,from oldest to most recent?

Accepted Answer

The correct order of geological periods, from oldest to most recent, is Cambrian, Devonian, Permian, and Cretaceous. Option A lists the periods in this correct sequence. Option B and D have incorrect orders, while option C has omitted the Devonian period.

Question 20

How were conditions on the early Earth of more than 3 billion years ago different from those on today's Earth?

Accepted Answer

The answer of How were conditions on the early Earth...

Quiz 25: The History of Life on Earth