Ch 13 Mastering HW

Why would it be highly advantageous to a cell to form a mutualism (and eventually an endosymbiotic association) with a prokaryote capable of aerobic cellular respiration?

Aerobic cellular respiration involves an electron transport chain with oxygen as the terminal electron acceptor. This produces large amounts of ATP as the electron transport chain produces the greatest amount of ATP in cellular respiration.

Why is visualization not sufficient to properly identify bacteria?

Bacteria have a limited set of shapes and many unrelated bacteria share the same shape.

Which statements describe the evidence that supports the endosymbiotic theory?

Chloroplasts and mitochondria have a double-stranded, circular piece of DNA in their cytoplasm.

The first question in this dichotomous key addresses

Gram stain differences.

Which of the following is an assumption used in the molecular clock approach? a. Nucleotide changes are NOT random. b. Nucleotide changes are subject to intense selective pressure. c. Nucleotide changes accumulate in a sequence in proportion to time. d. Nucleotide changes are generally NOT transferred to progeny.

Nucleotide changes accumulate in a sequence in proportion to time.

It is hypothesized that early photosynthesis was anoxygenic. If so, what was the effect of the appearance of organisms using oxygenic photosynthesis?

Organisms using oxygenic photosynthesis release oxygen into the atmosphere, causing an increase in the oxygen in the atmosphere and allowing for the development of aerobes.

Microbial species have a core genome and a pan genome. What is the difference between the two?

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.

Some organisms seem to change names, for example Vibrio fischerii is now Aliivibrio fischerii. How can it be known which is the proper name?

The official source is the International Journal of Systematic and Evolutionary Microbiology. Bergey's Manual is a good resource for taxonomy, but not always for the most recent changes in nomenclature.

Why are flowcharts useful for dichotomous keys?

They allow the researcher to visualize relationships between different bacteria.

What is the hallmark of dichotomous keys?

They consist of a series of paired statements, in which only one statement of each pair applies to a given organism.

How many answers are there to a question in a dichotomous key flowchart?

Two

Molecular sequencing suggests that mitochondria arose from a group of prokaryotic organisms within the a. Alphaproteobacteria. b. Crenarchaeota. c. cyanobacteria. d. iron-oxidizing bacteria.

a. Alphaproteobacteria.

Which of the following best explains the endosymbiont hypothesis? a. Prokaryotes capable of cellular respiration and prokaryotes capable of photosynthesis took up residence in larger prokaryotes, forming obligate mutualisms. The prokaryotes capable of cellular respiration evolved into mitochondria and the prokaryotes capable of photosynthesis evolved into chloroplasts. b. Prokaryotes capable of cellular respiration began to associate with prokaryotes capable of photosynthesis. They fused together to form eukaryotic cells. c. Prokaryotes capable of cellular respiration and prokaryotes capable of photosynthesis took up residence in larger prokaryotes, forming obligate mutualisms. The prokaryotes capable of cellular respiration evolved into chloroplasts and the prokaryotes capable of photosynthesis evolved into mitochondria. d. Prokaryotes capable of digestion took up residence in larger prokaryotes, forming obligate mutualisms. The prokaryotes capable of digestion evolved into lysosomes.

a. Prokaryotes capable of cellular respiration and prokaryotes capable of photosynthesis took up residence in larger prokaryotes, forming obligate mutualisms. The prokaryotes capable of cellular respiration evolved into mitochondria and the prokaryotes capable of photosynthesis evolved into chloroplasts.

What is one piece of evidence that supports the RNA world hypothesis? a. RNAs can have catalytic activity. b. There are traces of RNA that have been dated and found to be older than any traces of DNA. c. RNA is more stable than DNA and therefore more likely to have been able to exist in such a harsh environment. d. Early cells relied more heavily on RNA than on DNA.

a. RNAs can have catalytic activity. (RNAs can have catalytic activity (e.g., ribozymes) and are important cofactors and components of many molecules in living cells.)

Evolution is driven by a. selection pressure applied to random mutation. b. novel metabolic pathways. c. random mutation. d. selection pressure.

a. selection pressure applied to random mutation.

Microorganisms were probably restricted to the oceans and subsurface environments until a. the ozone layer was made. b. chemoorganotrophy developed. c. aquatic life brought them onto land. d. phototrophy evolved.

a. the ozone layer was made.

Phylogenetic trees for bacteria are constructed by which of the following?

analyzing molecular similarities and then using computer algorithms or optimality criteria to construct phylogenetic trees showing hypothesized evolutionary relationships

Biochemical tests _________________.

are the main methods used to identify unknown bacteria

Horizontal gene transfer a. occurs within bacterial species. b. complicates the construction of phylogenetic trees and the interpretation of specific traits in relation to evolution. c. is so rare over evolutionary history that it is not considered when examining microbial evolution. d. only affects the evolution of plasmids.

b. complicates the construction of phylogenetic trees and the interpretation of specific traits in relation to evolution.

A change in allele frequencies in a set of organisms over time is called __________. a. selection b. evolution c. mutation d. fitness

b. evolution

What was the LUCA? a. the type of prokaryote that evolved into a eukaryote b. the last organism prior to the divergence of bacteria and archaea c. the last eukaryote before eukaryotes diversified d. the first cellular organism to evolve

b. the last organism prior to the divergence of bacteria and archaea

For organisms to be considered members of the same species, they must __________.

be genetically and phenotypically cohesive

Which of the following populations would be most likely to demonstrate genetic drift? Hint: Genetic drift refers to the process by which gene frequencies can change due to random factors. a. A large population of bacteria is grown over an extended period in a continuous culture system. b. Someone takes an extended course of antibiotics, leaving a relatively small number of surviving bacteria. c. A researcher transfers bacteria into fresh medium but accidentally collects only a very small quantity of bacteria in the process. d. A researcher performs a Gram stain to separate gram-positive and gram-negative bacteria. He places the gram-positive bacteria in one test tube and the gram-negative bacteria in the other.

c. A researcher transfers bacteria into fresh medium but accidentally collects only a very small quantity of bacteria in the process. Why it's not b: The antibiotics killed many of the bacteria present, selecting those that were more resistant (in other words, selecting those that had higher fitness in that environment). The process was not random, so it is not an example of genetic drift.

It is hypothesized that early photosynthesis was anoxygenic. Think about the role of oxygen in photosynthesis as carried out by green plants, green algae, and cyanobacteria (as opposed to modern organisms that use anoxygenic photosynthesis). What would have been different in anoxygenic photosynthesis (or is different in modern organisms that use anoxygenic photosynthesis)? a. Anoxygenic organisms would not have been able to produce ATP, only NADPH. b. Anoxygenic organisms do not require light while oxygenic organisms do require light. c. Green plants, green algae, and cyanobacteria split H2O to replace an excited electron in noncyclic photophosphorylation. Oxygen is released into the atmosphere. In anoxygenic photosynthesis, a different molecule (such as H2S) is split and a different product (such as sulfur) is released. d. Anoxygenic organisms would have been able to produce only NADPH, not ATP.

c. Green plants, green algae, and cyanobacteria split H2O to replace an excited electron in noncyclic photophosphorylation. Oxygen is released into the atmosphere. In anoxygenic photosynthesis, a different molecule (such as H2S) is split and a different product (such as sulfur) is released.

Photosynthetic organisms were present when Earth was primarily anoxic. Why was the appearance of cyanobacteria critical for the oxidation of the atmosphere? a. Cyanobacteria carry out anoxic photosynthesis. b. The early forms of photosynthesis were carried out in the water, and there was no way for the oxygen to move into the atmosphere. c. The early forms of photosynthesis did not produce oxygen as a waste product. d. The early forms of photosynthesis did produce oxygen, but it was not enough to make a difference in the atmosphere.

c. The early forms of photosynthesis did not produce oxygen as a waste product.

The earliest RNA probably functioned in a. self-replication. b. catalysis. c. both catalysis and self-replication. d. neither catalysis nor self-replication.

c. both catalysis and self-replication.

Compared with today, the temperature on Earth during its first half-billion years was probably

considerably warmer.

Scientists believe life may have begun in an RNA world because __________. a. RNA is essential to processes found in all cells b. RNA can have catalytic activity c. RNA can bind to small molecules, such as nucleotides d. All of the listed responses are correct.

d. All of the listed responses are correct.

Which of the following is NOT evidence that mitochondria originated as independent prokaryotes, as stated by the endosymbiont hypothesis? a. Mitochondria have ribosomes that are the same size as prokaryotic ribosomes. b. Phylogenetic analyses place mitochondrial ribosomal RNA sequences within a bacterial phylum. c. Mitochondria have circular DNA that resembles that of prokaryotes. d. Mitochondria have a membrane that includes peptidoglycan.

d. Mitochondria have a membrane that includes peptidoglycan.

According to the RNA world hypothesis, which of the following was the correct sequence of developments? a. biological building blocks (e.g., amino acids, sugars, and nucleosides), then DNA, then RNA (including catalytic and self-replicating RNA), then protein synthesis, then lipid bilayers surrounding early cellular life b. biological building blocks (e.g., amino acids, sugars, and nucleosides), then lipid bilayers surrounding these building blocks, then RNA (including catalytic and self-replicating RNA), then protein synthesis, then DNA c. biological building blocks (e.g., amino acids, sugars, and nucleosides), then RNA (including catalytic and self-replicating RNA), then DNA, then protein synthesis, then lipid bilayers surrounding early cellular life d. biological building blocks (e.g., amino acids, sugars, and nucleosides), then RNA (including catalytic and self-replicating RNA), then protein synthesis, then DNA, then lipid bilayers surrounding early cellular life

d. biological building blocks (e.g., amino acids, sugars, and nucleosides), then RNA (including catalytic and self-replicating RNA), then protein synthesis, then DNA, then lipid bilayers surrounding early cellular life

A monophyletic group is a group that

descended from one ancestor.

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

each accumulate different random mutations resulting in different adaptations to use the nitrogen in the media.

Multilocus sequence typing (MLST) involves sequencing several different

housekeeping genes.

Both deletions and insertions occur during the evolution of microbial genomes. Insertions bring in new genes that may be useful for the cell. Deletions

may increase fitness of a microorganism by eliminating unneeded genes.

Two eukaryotic organelles that are hypothesized to be the result of endosymbiosis are the ________ and the ________.

mitochondrion / chloroplast

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?

multilocus sequence typing

As oxygen appeared in the atmosphere, ________ also accumulated, which formed a protective barrier that protects the Earth from ________.

ozone / UV radiation

One widely used 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.

parsimony

A method of genetic fingerprinting that relies on the location of small subunit rRNA genes on DNA fragments is called __________.

ribotyping

The oxic atmosphere created conditions that led to the evolution of various new metabolic pathways, such as

sulfide oxidation, nitrification, and iron oxidation.

LUCA is

the last universal common ancestor.

The genes for 16S rRNA are used to determine genetic relatedness amongst microbes because __________.

these highly conserved genes are of adequate length to show deep relationships