Deck 17: The Origins of Life and Precambrian Evolution

Question 1

Lateral gene transfer means that phylogenetic analyses of different individual genes from the same set of organisms often yield results that are inconsistent with each other.What technique seems to avoid this problem and give us the clearest,most consistent view of the "tree of life"?

A) the polymerase chain reaction (PCR)
B) molecular clock analyses
C) "shotgun" rRNA sequencing from environmental samples
D) Bayesian phylogenetic reconstruction
E) whole-genome phylogenetic analysis

Answer 1

E

Question 2

James Ferris discovered that clay minerals are capable of ________.

A) joining pyrimidines to simple sugars
B) catalyzing the polymerization of activated nucleotides
C) breaking down biomolecules to release energy
D) activating nucleotides by adding phosphate groups
E) forming microscopic spheres from short polymers of amino acids

Answer 2

B

Question 3

Could a varying,self-replicating population of RNA molecules be considered alive?

A) No, because such a population would not be contained inside a cell.
B) Yes, because such a population would show variation, inheritance, and selection.
C) No, because RNA molecules are not subject to selection.
D) Yes, because RNAs code for proteins that can then replicate the RNAs.
E) No, because ribonucleotides are not suited for energy transfer functions.

Answer 3

B

Question 4

Carl Woese has controversially proposed that all three domains of life evolved from a(n)________.

A) single last unique common ancestor (LUCA)
B) extremophilic archaean
C) fusion of a bacterium with an archaean
D) universal gene-exchange pool
E) very large virus

Question 5

The earliest fossil records of bacteria-like organisms,dated at over 3 billion years,________.

A) are too spotty to allow us to trace lines of descent to present-day organisms
B) unquestionably belong to cyanobacteria
C) show that early cells had membranes made of short amino acid chains
D) used only RNA molecules for both information storage and chemical catalysis
E) already contained endosymbiotic organelles

Question 6

Carl Woese is BEST known for discovering that ________.

A) eukaryote membrane-bound organelles are descended from endosymbionts
B) the oldest fossils are 3.4 billion years old
C) prokaryotes comprise two very different branches: Bacteria and Archaea
D) energy acting on gases and water vapor will create a "primordial soup" of organic molecules
E) the last universal common ancestor (LUCA) did not have DNA-dependent RNA polymerase

Question 7

A famous experiment that generated organic molecules from a mixture of gases thought to resemble the early Earth's atmosphere was carried out in 1953 by ________.

A) Stanley Miller
B) Charles Darwin
C) Thomas Cech
D) J. S. Haldane
E) Aniela Wochner

Question 8

The organisms formerly classified in the Kingdom Protista ________.

A) all contain chloroplasts
B) form a single monophyletic group
C) include the last universal common ancestor (LUCA) of life
D) are scattered throughout all branches of the eukaryote family tree
E) have a fossil record extending back 3.4 million years

Question 9

The minimum age of the LUCA (last unique common ancestor)is the age of the oldest fossils that can be identified with certainty as close relatives of present-day prokaryotes and eukaryotes.Such fossils are about ________.

A) 3.8 billion years old
B) 2 billion years old
C) 542 million years old
D) 3.28 billion years old
E) 65 million years old

Question 10

Which of these is NOT an evolutionary advantage of the first cell membranes?

A) Membranes allow cells to move independently.
B) Membranes allow for cells to be compartmentalize.
C) Membranes allow substances to be concentrated inside a cell, or pumped outside.
D) Membranes allow genotypes and the phenotypes they produce to stay linked.
E) All of the above are advantages of cell membranes.

Question 11

The Murchison meteorite was a significant discovery for the study of the origin of life,because it ________.

A) contained self-replicating organisms
B) contained carbon, hydrogen, nitrogen, and oxygen
C) contained significant amounts of amino acids
D) contained short lengths of RNA
E) descended through the atmosphere slowly enough that friction was negligible

Question 12

The model of life's origins,which posits that all of the necessary ingredients for the origin of life were present on early Earth,has been named after two early twentieth-century scientists.This model is called the ________ [two words] model.

Question 13

Minick Rosing's analysis of microscopic globules of carbon found in rocks 3.7 billion years old showed that they were somewhat higher in ¹²C as opposed to ¹³C.This is significant because ________.

A) ¹³C radiometrically decays into ¹²C, which lets us calculate the age of these rocks
B) life could not have arisen in an environment with excessive ¹³C
C) these carbon globules contain visible remains of cell walls and nuclei
D) living things that fix carbon preferentially incorporate ¹²C over ¹³C
E) meteorites must have brought ¹³C to the early Earth

Question 14

A problem with the basic Oparin-Haldane model for the origin of life (though not necessarily an unsolvable one)is that ________.

A) it does not explain the origin of chirality
B) the early Earth is now not thought to have had a highly reducing atmosphere
C) monomers have to be chemically activated before they will polymerize
D) purine bases can attach to sugars in many equally probable ways
E) All of the above.

Question 15

According to Patrick Forterre's hypothesis,viruses are ultimately responsible for ________.

A) introducing DNA into the ancestors of Bacteria, Archaea, and Eucarya
B) fusing with a bacterium and giving rise to the eukaryote nucleus
C) introducing information-processing genes into the ancestral chronocytes
D) enabling Archaea to withstand extreme environmental conditions causing mass extinctions

Question 16

The gene that encodes small-subunit ribosomal RNA is useful for reconstructing the phylogeny of all organisms,because ________.

A) the gene is subject to strong stabilizing selection
B) the gene's function has stayed unchanged in all organisms
C) all organisms have ribosomes with similar composition and structure
D) all organisms have the gene
E) All of the above.

Question 17

The accompanying figure shows the history of large meteorite impacts on both the earth and the moon.What is the graph's major implication for the origin of life on Earth?

A) Huge impacts make it unlikely that life arose and survived on Earth before about 3.8 billion years ago.
B) Meteorites could not have brought the organic molecules that were necessary for life appear.
C) The moon is considerably older than the Earth.
D) Life must have originated on a different body in the solar system and been brought to Earth.
E) The Oparin-Haldane model of life's origins applies to the moon as well as to the Earth.

Question 18

Proteins carry out much of the biochemistry of life,including DNA replication,but DNA stores the information needed to build correct proteins.Early life forms would have needed both proteins and DNA,but neither can exist without the other.The RNA world hypothesis is an appealing solution to this problem,because it states that ________.

A) RNA can evolve into DNA by natural selection
B) proteins can store the information needed for their own synthesis
C) RNA is more chemically stable than DNA
D) nucleotides of RNA are chemically similar to amino acids
E) some RNA molecules both store information and catalyze chemical reactions

Question 19

Important molecular discoveries in the 1980s have led researchers to hypothesize that the original,vital organic molecule shaping living things was not what was first thought.What molecule is currently supported as the candidate for the vital molecule for early life?

Question 20

Deductive reasoning generates the conclusion that because we are here to think about and ask questions about the first living thing on Earth,it must have existed.This first living thing presumably gave rise to multiple lineages,at least one of which served as the ancestor for all of life on Earth.The acronym IDA has been applied to the first living thing,and LUCA to the ancestor that gave rise to all of life.What do IDA and LUCA stand for?

Question 21

Fossil evidence suggests that the latest possible date for root of the universal phylogeny predates the ________ billion-year mark.

Question 22

In attempting to construct a universal phylogeny,researchers analyzed several different gene sets.The results of this analysis are not congruent (see accompanying figure).The most likely explanation for this,as proposed by Carl Woese and others,is ________ [three words] in early populations,which would account for these discrepancies.

Question 23

Analysis of the sequences of the small subunit rRNA generated a shift in our current taxonomic scheme,with the addition of three levels called domains.What are the three domains?

Question 24

An estimate of the universal phylogeny,based on the small subunit rRNA,is reproduced in the accompanying figure.According to this reconstruction,the domain that Eucarya shares the most recent common ancestor with is ________.

Question 25

After important molecular discoveries in the 1980s,researchers have shifted their attention to RNA as the founding organic molecule for all of life on Earth ("The RNA World").What attributes does RNA have,and what evidence has been generated to support this hypothesis?

Question 26

The authors of your textbook suggest that,"for genes shared among all organisms…Animals,Plants,and Fungi appear to possess less than 10% of the nucleotide-level diversity observed on Earth." Given the relatively recently generated phylogenies such as those in the accompanying figures,along with what you know about the history of life on this planet,does this seem like a reasonable statement? Explain.

Question 27

The Oparin-Haldane model of the origins of life on Earth can be concisely elucidated in three stages.Identify and describe each stage in the context of what is currently known,as well as what has been hypothesized,about the conditions of early Earth.

Question 28

It is now thought that the last common ancestor of the three domains was not a single lineage.Rather,it was ________.

Question 29

Estimates of the age of Earth,taken from meteorites,date our planet to be approximately ________ years old.The BEST estimate of when life emerged,based on extrapolation of known and verifiable fossils,is approximately ________ years ago.In essence,then,life emerged approximately ________ years after Earth formed.

Question 30

The authors of your textbook maintain that "the ability to store and transmit information (genotype)and the ability to express that information (phenotype)are perhaps the most important criteria that set life apart from nonlife." When we compare this statement to Darwin's four natural selection postulates (variation,inheritance,excess reproduction,and differential survival and reproduction),interesting parallels emerge.Evaluate the authors' claim in the context of Darwinian evolution by natural selection.

Question 31

The explanation linking viruses to the origin of the three domains,which includes the conversion of cellular genomes from RNA to DNA,is known as the ________.