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level: Level 1

Questions and Answers List

level questions: Level 1

Question	Answer
The earliest stromatolites were probably formed by A) anoxygenic phototrophs. B) anoxygenic lithotrophs. C) oxygenic phototrophs. D) oxygenic lithotrophs.	A) anoxygenic phototrophs.
What two gases were most abundant on early Earth? A) O2 and CO2 B) N2 and H2 C) CO2 and H2 D) CO2 and N2	C) CO2 and H2
Compared with today, the temperature on Earth during its first half-billion years was probably A) considerably warmer. B) considerably colder. C) about the same as today. D) about the same as today on average, but the diurnal fluctuations were much greater.	A) considerably warmer.
The earliest RNA probably functioned in A) catalysis. B) self-replication. C) both catalysis and self-replication. D) neither catalysis nor self-replication	C) both catalysis and self-replication.
Chemical reactions involving ________ have been proposed as energy-yielding reactions for primitive organisms. A) Fe, O2, and H2 B) S, O2, and H2 C) S, and O2 D) S, and H2	D) S, and H2
Evolution is driven by A) random mutation. B) novel metabolic pathways. C) selection pressure. D) selection pressure applied to random mutation.	D) selection pressure applied to random mutation.
Microorganisms were probably restricted to the oceans and subsurface environments until A) aquatic life brought them onto land. B) chemoorganotrophy developed. C) phototrophy evolved. D) the ozone layer was made.	D) the ozone layer was made.
Which of the following is an assumption used in the molecular clock approach? A) Nucleotide changes accumulate in a sequence in proportion to time. B) Nucleotide changes are generally NOT transferred to progeny. C) Nucleotide changes are NOT random. D) Nucleotide changes are subject to intense selective pressure.	A) Nucleotide changes accumulate in a sequence in proportion to time.
The most widely used molecule in sequence-based evolutionary analyses are ________ genes. A) ATPase B) electron transport C) SSU rRNA D) tRNA	C) SSU rRNA
A monophyletic group is a group that A) descended from one ancestor. B) has the same fitness level. C) possesses one taxonomic trait that is the same. D) shares one phylogenetic marker.	A) descended from one ancestor.
A sequence variant of a gene is called a(n) A) allele. B) mutation. C) nucleotide polymorphism. D) ribotype.	A) allele.
A key concept in evolution is that all mutations are A) random. B) neutral. C) deleterious. D) either deleterious or beneficial.	A) random.
LUCA is A) the last universal common ancestor. B) the individual ancestor of each of the three domains. C) actually somewhat of a misnomer because it is now believed that each of the domains arose independently. D) All of the answers are correct.	A) the last universal common ancestor.
Horizontal gene transfer A) is so rare over evolutionary history that it is not considered when examining microbial evolution. B) occurs within bacterial species. C) complicates the construction of phylogenetic trees and the interpretation of specific traits in relation to evolution. D) only affects the evolution of plasmids.	C) complicates the construction of phylogenetic trees and the interpretation of specific traits in relation to evolution.
Molecular sequencing suggests that mitochondria arose from a group of prokaryotic organisms within the A) Crenarchaeota. B) cyanobacteria. C) iron-oxidizing bacteria. D) Proteobacteria	D) Proteobacteria.
Which statement most closely expresses our present understanding? A) The chloroplast is an ancestor of the cyanobacteria. B) The cyanobacteria are descendents of the chloroplast. C) The chloroplast arose from the incorporation of a cyanobacterial-like organism. D) The chloroplast and the cyanobacteria are not closely (or specifically) related.	C) The chloroplast arose from the incorporation of a cyanobacterial-like organism.
Two tubes are inoculated from one test tube of a bacterial culture. The cultures are then transferred every day for 2 months. All of the media and growth conditions are the same in every tube. After 2 months of cultivation, the fitness and genotype frequencies of the populations in the two tubes are compared. The fitness of the two cultures is the same, but the genotype frequencies are very different in the two cultures. How is this possible? A) Two months is not long enough for different fitness levels to evolve even if the genotype frequencies change. B) This result is not possible because different genotype frequencies would result in different fitness levels under the same growth conditions. C) Natural selection caused the evolution of different genotype frequencies within the separate test tubes. D) Genetic drift within the small populations in the test tubes resulted in different genotype frequencies.	D) Genetic drift within the small populations in the test tubes resulted in different genotype frequencies.
If you allowed 10 identical parallel Salmonella cultures to evolve for 10,000 generations under new growth conditions with very little nitrogen, the parallel cultures would A) evolve identical adaptations to use the nitrogen source provided in the media. B) not change or adapt very much over this small number of generations. C) each accumulate different random mutations resulting in different adaptations to use the nitrogen in the media. D) direct mutations to occur in nitrogen utilization and uptake genes in order to adapt rapidly to the culture conditions.	C) each accumulate different random mutations resulting in different adaptations to use the nitrogen in the media.
Both deletions and insertions occur during the evolution of microbial genomes. Insertions bring in new genes that may be useful for the cell, but deletions A) may increase fitness of a microorganism by eliminating unneeded genes. B) always result in a severe loss of fitness for the microorganism. C) are uncommon because they are usually lethal. D) always result in a severe loss of fitness but keep microbial genomes compact.	A) may increase fitness of a microorganism by eliminating unneeded genes.
Polyphasic taxonomy uses methods that include A) phenotypic methods. B) genotypic methods. C) phylogenetic methods. D) phenotypic, genotypic, and phylogenetic methods.	D) phenotypic, genotypic, and phylogenetic methods.
Ribotyping A) bypasses sequencing and sequence alignments. B) exploits unique DNA restriction patterns. C) allows discrimination between species and different strains of a species. D) bypasses sequencing and sequence alignments, exploits unique DNA restriction patterns, and allows discrimination between species and different strains of a species.	D) bypasses sequencing and sequence alignments, exploits unique DNA restriction patterns, and allows discrimination between species and different strains of a species.
Which is NOT a characteristic of a "primitive" state of microbial evolution? A) hyperthermophilic B) aerobic metabolism C) small genome D) branching near the root of the evolutionary tree of life	B) aerobic metabolism
Because DNA:DNA hybridization reveals subtle differences in genes, it is useful for differentiating organisms from different A) domains. B) families. C) orders. D) strains or species.	D) strains or species.
Which taxonomic tool would scientists use if they wanted to determine if an outbreak of food poisoning was caused by a particular strain of a pathogen? A) fluorescence in situ hybridization B) DNA:DNA hybridization C) multilocus sequence typing D) fatty acid methyl ester analysis	C) multilocus sequence typing
It is believed that phototrophy arose approximately 3.3 billion years ago in A) Bacteria. B) Archaea. C) Eukarya. D) LUCA.	A) Bacteria.
The oxic atmosphere created conditions that led to the evolution of various new metabolic pathways, such as A) sulfide oxidation. B) nitrification. C) iron oxidation. D) sulfide oxidation, nitrification, and iron oxidation.	D) sulfide oxidation, nitrification, and iron oxidation.
You are studying 12 new isolates from the human skin. The isolates have 16S rRNA sequences that are 97% similar and share important phenotypic traits. Their genomes have 55% of their genes in common. The isolates would most likely be A) classified as individual strains of the same species. B) classified as individual species of the same genus. C) split into different families. D) classified as the same species if they can mate via conjugation.	A) classified as individual strains of the same species.
The pan genome of a microbial species is constantly changing because of A) bottleneck events. B) horizontal gene transfer. C) substitutions. D) substitution and bottleneck events.	B) horizontal gene transfer.
Microbial ________ studies the diversity of microorganisms and links their phylogeny with ________. A) taxonomy / genotype B) phylogeny / phenotype C) taxonomy / phenotype D) systematics / taxonomy	D) systematics / taxonomy
What was produced by photosynthesis before the cyanobacterial lineage developed on Earth? A) oxygen B) elemental sulfur C) ferrous iron D) hydrogen sulfide	B) elemental sulfur
Based on the phylogenetic tree below, which of the following statements is FALSE? A) Species E is more closely related to species A than to species D. B) Species D is more closely related to species C than to species E. C) Species F is more closely related to species D than to species E. D) Species C is more closely related to species B than to species D.	B) Species D is more closely related to species C than to species E.
The early energy reactions used hydrogen, which is a powerful ________ and could have been used to form ________. A) oxidant / the proton motive force B) electron donor / the proton motive force C) electron acceptor / oxygen D) oxidant / oxygen	B) electron donor / the proton motive force
Oxygen did not accumulate in the early atmosphere until it reacted with reduced materials, especially ________, in the oceans. A) hydrogen B) elemental sulfur C) ferrous iron D) nitrate	C) ferrous iron
As oxygen appeared in the atmosphere, ________ also accumulated, which formed a protective barrier that protects the Earth from ________. A) ozone / UV radiation B) elemental sulfur / volcanism C) ferrous iron / hydroxylating radicals D) sulfate / hydrogen sulfide	A) ozone / UV radiation
Two eukaryotic organelles that are hypothesized to be the result of endosymbiosis are the ________ and the ________. A) nucleus / Golgi body B) mitochondrion / chloroplast C) endoplasmic reticulum / Golgi body D) hydrogenosome / chloroplast	B) mitochondrion / chloroplast
Microbial species have a core genome and a pan genome. What is the difference between the two? A) The core genome consists of all the nucleic acid polymerases and translation enzymes, while the pan genome consists of all the biosynthetic pathways. B) The core genome is the set of genes within the mitochondria, while the pan genome is the set of genes in the nucleus of a species. C) The core genome is a set of genes shared by all members of a species, while the pan genome includes the core genes as well as genes that are not shared by all members. D) The core genome is the set of genes introduced by horizontal gene transfer, while the pan genome is the set of genes that is not transferred horizontally.	C) The core genome is a set of genes shared by all members of a species, while the pan genome includes the core genes as well as genes that are not shared by all members.
What characteristics make a gene a good candidate for determining the evolutionary relationships between organisms? A) highly conserved B) universally distributed C) transferred horizontally between species D) highly conserved and universally distributed	D) highly conserved and universally distributed
Which of the following statements is FALSE concerning the universal tree of life? A) Previous versions of the universal tree of life were based largely on fossils and comparative biology, which overlooked the diversity of and relationships between most prokaryotes. B) The current universal tree of life is supported by multiple genes including SSU rRNA sequences. C) The current universal tree of life depicts three domains of life, two of which are prokaryotic. D) The current universal tree of life is based on molecular sequences and completely changes our view of evolutionary relationships between eukaryotic species.	D) The current universal tree of life is based on molecular sequences and completely changes our view of evolutionary relationships between eukaryotic species.
________ formed the semipermeable membrane-like surfaces for the earliest life forms. A) Proteins B) Hydrogen sulfide C) Lipid bilayers D) RNA	C) Lipid bilayers
The first catalytic and self-replication biological molecule was most likely A) RNA. B) DNA. C) proteins. D) ATP.	A) RNA.
The evolutionary history of a group of organisms is called its ________ and it is inferred from ________. A) taxonomy / phenotype B) phylogeny / nucleotide sequence data C) phylogeny / phenotype D) taxonomy / morphology	B) phylogeny / nucleotide sequence data
One widely used cladistic method of examining evolutionary relationships is ________, which is based on the assumption that evolution is most likely to have proceeded by the path requiring fewest changes. A) topology B) neighbor joining C) parsimony D) systematics	C) parsimony
Multilocus sequence typing involves sequencing several different A) genomes. B) housekeeping genes. C) tRNA genes. D) rRNA genes.	B) housekeeping genes.
Systematic analysis now commonly includes ________ to identify, characterize, and determine relationships between new strains of bacterial species. A) whole genome analysis B) microscopy C) staining D) pigments	A) whole genome analysis
The atmosphere of primitive Earth is usually classified as an oxidizing atmosphere.	FALSE
The earliest nucleic acid was probably a simple DNA molecule.	FALSE
The establishment of DNA as the genome of the cell may have resulted from the need to store genetic information in a more stable form than RNA.	TRUE
Eukaryotes originated after the rise in atmospheric oxygen.	TRUE
Two organisms containing identical GC ratios are not necessarily related.	TRUE
Sequencing technology and molecular phylogenetic analyses have had very little impact on our understanding of the evolution and diversity of life on Earth.	FALSE
Prior to rRNA sequencing and the use of molecular phylogeny, Bacteria and Archaea were classified as in a single group of simple organisms called the Monera.	TRUE
The domains of life arose as barriers between gene exchange evolved between organisms.	TRUE
Microbial species are difficult to define because they are often polyphyletic.	FALSE
Most bacterial phyla lack strong phenotypic cohesiveness.	TRUE
At present there are four phyla in the domain Bacteria.	FALSE
The hyperthermophilic members of the Crenarchaeota branch very close to the root of the universal tree.	TRUE
The 16S rRNA sequence is an approximately 1,500 bp linear strand of single stranded RNA.	FALSE
) DNA:DNA hybridization is a sensitive method for revealing subtle genetic differences because it measures the degree of sequence similarity between two genomes.	TRUE
One phenotypic trait used for species identification and description is the analysis of the types and proportions of the fatty acids present in the cytoplasmic and outer membranes. The methodology employed is often nicknamed FAME.	TRUE
In taxonomy, family is a more general term than order.	FALSE
Oxygen was a driving factor in the formation of eukaryotic cells.	TRUE
The primary domains were founded based on comparative ribosomal RNA gene sequencing.	TRUE
All unicellular organisms belong to the same domain of life.	FALSE
Approximately 4 billion years ago Archaea and Bacteria diverged as being distinct from each other.	TRUE
When exposed to UV light, oxygen gas produces ozone gas.	TRUE
Lateral gene transfer is one plausible explanation as to why organisms in Archaea, Bacteria, and Eukarya still share so many genes among such distinct domains.	TRUE