Question 1

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

The correct sequence starts with the origin of cyanobacteria, which are among the earliest forms of life on Earth. Following this, the origin of mitochondria and chloroplasts through endosymbiotic events occurred, leading to the development of complex eukaryotic cells. Multicellular eukaryotes then evolved, and finally, symbiotic relationships such as fungal-plant symbioses developed.

Question 2

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 3

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

Accepted Answer

A

Question 4

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 fact that RNA molecules serve as primers for DNA synthesis suggests that earlier genetic systems based on RNA existed before the development of DNA. This supports the hypothesis that RNA was the first genetic material on Earth.

Question 5

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

Accepted Answer

Soft-bodied organisms, like worms, are less likely to fossilize because they lack hard parts that are more easily preserved.

Question 6

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

Accepted Answer

RNA was capable of self-replication and carrying out catalytic functions, indicating that it was likely the first genetic material. DNA is structurally more stable but lacks the catalytic capabilities of RNA. The other choices (A, B, C, and E) do not provide strong evidence in favor of RNA as the first genetic material.

Question 7

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 most widely accepted sequence of events in the origin of life is the synthesis of organic monomers (II) followed by the synthesis of organic polymers (III), leading to the formation of protobionts (I). Only after these events did the formation of DNA-based genetic systems (IV) occur. Choice C is the correct sequence in the given options.

Question 8

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 9

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

Accepted Answer

The oldest fossilized cells on Earth resemble prokaryotic cells, providing the strongest evidence that prokaryotes evolved before eukaryotes.

Question 10

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 is currently the most problematic question in the origin of life research. This is because it would provide insight into how the genetic code arose and how complexity evolved. It would also help us understand how life went from simple RNA molecules to fully functioning cells.

Question 11

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, such as from reptilian-like teeth to more complex molars with cusps and ridges. This is evidence of the gradual evolution of mammals from their reptilian ancestors. None of the other answer options are supported by the fossil record of mammalian origins.

Question 12

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 13

The first genes on Earth were probably

Accepted Answer

The most widely accepted hypothesis for the first genes on Earth is that they were auto-catalytic RNA molecules. This is supported by experiments that have shown that RNA molecules can replicate themselves and catalyze chemical reactions, suggesting that RNA could have played both a genetic and catalytic role in early life. The other options involve DNA or oligopeptides, which are believed to have evolved later in the history of life on Earth.

Question 14

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 15

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 16

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

Accepted Answer

The fossil record extends back approximately 3.5 billion years, to the beginning of life on Earth.

Question 17

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

Accepted Answer

A defining characteristic that all protobionts had in common is a surrounding membrane or membrane-like structure. This allowed for separation from the external environment and the ability to concentrate molecules and energy within the protobiont. The other answer choices may have been present in some protobionts, but not all and therefore are not defining characteristics for all protobionts.

Question 18

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 19

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

Accepted Answer

The release of oxygen gas by plant and bacterial photosynthesis caused iron in ocean water and terrestrial rocks to rust (oxidize). This is evident in the formation of banded iron formations found in ancient rocks.

Question 20

What is true of the Cambrian explosion?

Accepted Answer

Recent studies have shown that some of the animal groups that were once thought to have exploded in diversity during the Cambrian may have actually had a longer evolutionary history, with more gradual diversification leading up to the explosion. Additionally, new fossil discoveries from even earlier time periods have pushed back the origin of some animal groups, suggesting that the Cambrian explosion was not a sudden appearance of life on Earth.

Quiz 25: The History of Life on Earth

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