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42) If the vertical axis of Figure 27.1 refers to "Darwinian fitness," then which of the following is the
most valid and accurate measure of fitness?
A) number of daughter cells produced per mother cell per generation
B) amount of ATP generated per cell per unit time
C) average swimming speed of cells through the growth medium
D) amount of glucose synthesized per unit time
E) number of generations per unit time
43) If new genetic variation in the experimental populations arose solely by spontaneous mutations, then
the most effective process for subsequently increasing the prevalence of the beneficial mutations in the
population over the course of generations is
A) transduction.
B) binary fission.
C) conjugation.
D) transformation.
E) meiosis.
44) E. coli cells typically make most of their ATP by metabolizing glucose. Under the conditions of this
experiment, what should be true of E. coli's generation time (especially early in the course of the
experiment, but less so later on)?
A) Generation time should be the same as in the typical environment.
B) Generation time should be faster than in the typical environment.
C) Generation time should be slower than in the typical environment.
D) It is theoretically impossible to make any predictions about generation time under these conditions.
45) If the experimental population of E. coli lacks an F factor or F plasmid, and if bacteriophages are
excluded from the bacterial cultures, then which of these is (are) means by which beneficial mutations
might be transmitted horizontally to other E. coli cells?
A) via sex pili
B) via transduction
C) via conjugation
D) via transformation
E) Two of the responses above are correct.
Figure 27.2 depicts changes to the amount of DNA present in a recipient cell that is engaged in
conjugation with an Hfr cell. Hfr cell DNA begins entering the recipient cell at Time A. Assume that
reciprocal crossing over occurs (in other words, a fragment of the recipient's chromosome is exchanged
for a homologous fragment from the Hfr cell's DNA). Use Figure 27.2 to answer the following
questions.
Figure 27.2
46) What is occurring at Time C that is decreasing the DNA content?
A) crossing over
B) cytokinesis
C) meiosis
D) degradation of DNA that was not retained in the recipient's chromosome
E) reversal of the direction of conjugation
47) How is the recipient cell different at Time D than it was at Time A?
A) It has a greater number of genes.
B) It has a greater mass of DNA.
C) It has a different sequence of base pairs.
D) It contains bacteriophage DNA.
E) Its membrane-bound DNA pumps are inactive.
48) Which two processes are responsible for the shape of the curve at Time B?
1. transduction
2. entry of single-stranded Hfr DNA
3. rolling circle replication of single-stranded Hfr DNA
4. activation of DNA pumps in plasma membrane
A) 1 and 2
B) 1 and 4
C) 2 and 3
D) 2 and 4
E) 3 and 4
49) During which two times can the recipient accurately be described as "recombinant" due to the
sequence of events portrayed in Figure 27.2?
A) during Times C and D
B) during Times A and C
C) during Times B and C
D) during Times A and B
E) during Times B and D
50) Which question, arising from the results depicted in Figure 27.2, is most interesting from a genetic
perspective, and has the greatest potential to increase our knowledge base?
A) If reciprocal crossing over could occur even if the piece of donated Hfr DNA is identical to the
homologous portion of the recipient's chromosome, what prevents this from occurring?
B) What forces are generally responsible for disrupting the sex pilus?
C) How is it that a recipient cell does not necessarily become an Hfr cell as the result of conjugation
with an Hfr cell?
D) What makes a cell an Hfr cell?
51) The data were collected from the heterocysts of a nitrogen-fixing cyanobacterium inhabiting
equatorial ponds. Study the following graph and choose the most likely explanation for the shape of the
curve.
A) Enough O2 enters heterocysts during hours of peak photosynthesis to have a somewhat-inhibitory
effect on nitrogen fixation.
B) Light-dependent reaction rates must be highest between 1800 hours and 0600 hours.
C) Atmospheric N2 levels increase at night because plants are no longer metabolizing this gas, so they
are not absorbing this gas through their stomata.
D) Heterocyst walls become less permeable to N2 influx during darkness.
E) The amount of fixed nitrogen that is dissolved in the pond water in which the cyanobacteria are
growing peaks at the close of the photosynthetic day (1800 hours).
17
52) Consider the thermoacidophile, Sulfolobus acidocaldarius. Which of the following graphs most
accurately depicts the expected temperature and pH profiles of its enzymes? (Note: The horizontal axes
of these graphs are double, with pH above and temperature below.)
A)
B)
C)
D)
Scenario Questions
Use the information in the following paragraph to answer the next few questions.
A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the
intestinal lining. It adheres to the intestinal lining using a feature that also protects it from phagocytes,
bacteriophages, and dehydration. Fecal matter from a human in whose intestine this bacterium lives can
spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to
the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan.
53) This bacterium's ability to survive in a human who is taking penicillin pills may be due to the
presence of
1. penicillin-resistance genes
2. a secretory system that removes penicillin from the cell
3. a gram-positive cell wall
4. a gram-negative cell wall
5. an endospore
A) 1 or 5
B) 2 or 3
C) 4 or 5
D) 2, 3, or 5
E) 2, 4, or 5
54) Adherence to the intestinal lining by this bacterium is due to its possession of
A) fimbriae.
B) pili.
C) a capsule.
D) a flagellum.
E) a cell wall with an outer lipopolysaccharide membrane.
55) What should be true of the cell wall of this bacterium?
A) Its innermost layer is composed of a phospholipid bilayer.
B) After it has been subjected to Gram staining, the cell should remain purple.
C) It has an outer membrane of lipopolysaccharide.
D) It is mostly composed of a complex, cross-linked polysaccharide.
E) Two of the responses above are correct.
56) Some of the proteins that allow this bacterium to swim are related (in an evolutionary sense) to
proteins that
A) attach to the single chromosome.
B) act as restriction enzymes.
C) synthesize peptidoglycan for the cell wall.
D) move penicillin out of the cell.
E) comprise its ribosomes.
57) In which feature(s) should one be able to locate a complete chromosome of this bacterium?
1. nucleolus
2. prophage
3. endospore
4. nucleoid
A) 4 only
B) 1 and 3
C) 2 and 3
D) 3 and 4
E) 2, 3, and 4
58) The cell also lacks F factors and F plasmids. Upon its death, this bacterium should be able to
participate in
A) conjugation.
B) transduction.
C) transformation.
D) Three of the responses above are correct.
E) Two of the responses above are correct.
59) This bacterium derives nutrition by digesting human intestinal contents (in other words, food). Thus,
this bacterium should be an
A) aerobic chemoheterotroph.
B) aerobic chemoautotroph.
C) anaerobic chemoheterotroph.
D) anaerobic chemoautotroph.
60) This bacterium derives nutrition by digesting human intestinal contents (in other words, food).
Humans lacking this bacterium have no measurable reproductive advantage or disadvantage relative to
humans who harbor this bacterium. Consequently, the bacterium can be properly described as which of
the following?
1. symbiont
2. endosymbiont
3. mutualist
4. commensal
A) 4 only
B) 1 and 2
C) 1 and 4
D) 2 and 3
E) 2 and 4
Nitrogenase, the enzyme that catalyzes nitrogen fixation, is inhibited whenever free O2 reaches a critical
concentration. Consequently, nitrogen fixation cannot occur in cells wherein photosynthesis produces
free O2. Consider the colonial aquatic cyanobacterium, Anabaena, whose heterocytes are described as
having "…a thickened cell wall that restricts entry of O2 produced by neighboring cells. Intracellular
connections allow heterocysts to transport fixed nitrogen to neighboring cells in exchange for
carbohydrates."
61) Given that the enzymes that catalyze nitrogen fixation are inhibited by oxygen, what are two
"strategies" that nitrogen-fixing prokaryotes might use to protect these enzymes from oxygen?
1. couple them with photosystem II (the photosystem that splits water molecules)
2. package them in membranes that are impermeable to all gases
3. be obligate anaerobes
4. be strict aerobes
5. package these enzymes in specialized cells or compartments that inhibit oxygen entry
A) 1 and 4
B) 2 and 4
C) 2 and 5
D) 3 and 4
E) 3 and 5
62) Which two questions below arise from a careful reading of this quotation, and are most important for
understanding how N2 enters heterocysts, and how O2 is kept out of heterocysts?
1. If carbohydrates can enter the heterocysts from neighboring cells via the "intracellular connections,"
how is it that O2 doesn't also enter via this route?
2. If the cell walls of Anabaena's photosynthetic cells are permeable to O2 and CO2, are they also
permeable to N2?
3. If the nuclei of the photosynthetic cells contain the genes that code for nitrogen fixation, how can
these cells fail to perform nitrogen fixation?
4. If the nuclei of the heterocysts contain the genes that code for photosynthesis, how can these cells fail
to perform photosynthesis?
5. If the cell walls of Anabaena's heterocysts are permeable to N2, how is it that N2 doesn't diffuse out
of the heterocysts before it can be fixed?
6. If the thick cell walls of the heterocysts exclude entry of oxygen gas, how is it that they don't also
exclude the entry of nitrogen gas?
A) 1 and 3
B) 1 and 6
C) 2 and 5
D) 3 and 4
E) 4 and 6
The following table depicts characteristics of five prokaryotic species (A—E). Use the information in
the table to answer the following questions.
Trait
Species A
Species B
Species C
Species D
Species E
Plasmid
R
None
R
F
None
Gram Staining
Results
Variable
Variable
Negative
Negative
Negative
Nutritional Mode
Chemohetero-
troph
Chemoauto-
troph
Chemohetero-
troph
Chemohetero-
troph
Photoautotroph
Specialized
Metabolic
Pathways
Aerobic
methanotroph
(obtains carbon
and energy from
methane)
Anaerobic
methanogen
Anaerobic
butanolic
fermentation
Anaerobic lactic
acid fermentation
Anaerobic nitrogen
fixation and
aerobic
photosystems
I and II
Other Features
Fimbriae
Internal
membranes
Flagellum
Pili
Thylakoids
63) Which two species should have much more phospholipid, in the form of bilayers, in their cytoplasms
than most other bacteria?
A) species A and B
B) species A and C
C) species B and E
D) species C and D
E) species C and E
64) Which species should be able to respond most readily to taxes (plural of taxis)?
A) species A
B) species B
C) species C
D) species D
E) species E
65) How many of these species probably have a cell wall that partly consists of an outer membrane of
lipopolysaccharide?
A) only one species
B) two species
C) three species
D) four species
E) all five species
66) Gram-variable prokaryotes are, sometimes, those without any peptidoglycan. Which two species are
most likely to be archaeans?
A) species A and B
B) species A and C
C) species B and E
D) species C and D
E) species C and E
67) Species D is pathogenic if it gains access to the human intestine. Which other species, if it
coinhabited a human intestine along with species D, is most likely to result in a recombinant species that
is both pathogenic and resistant to some antibiotics?
A) species A
B) species B
C) species C
D) species D
E) species E
68) Which species might be able to include Hfr cells?
A) species A
B) species B
C) species C
D) species D
E) species E
69) Which species is most self-sustaining in terms of obtaining nutrition in environments containing
little fixed nitrogen or carbon?
A) species A
B) species B
C) species C
D) species D
E) species E
70) Which two species might be expected to cooperate metabolically, perhaps forming a biofilm wherein
one species surrounds cells of the other species?
A) species A and B
B) species A and C
C) species B and E
D) species C and D
E) species C and E
71) Which species is most likely to be found both in sewage treatment plants and in the guts of cattle?
A) species A
B) species B
C) species C
D) species D
E) species E
72) Which species is probably an important contributor to the base of aquatic food chains as a primary
producer?
A) species A
B) species B
C) species C
D) species D
E) species E
End-of-Chapter Questions
The following questions are from the end-of-chapter “Test Your Understanding” section in Chapter 27
of the textbook.
73) Genetic variation in bacterial populations cannot result from
A) transduction.
B) transformation
C) conjugation
D) mutation.
E) meiosis.
74) Photoautotrophs use
A) light as an energy source and CO2 as a carbon source.
B) light as an energy source and methane as a carbon source.
C) N2 as an energy source and CO2 as a carbon source.
D) CO2 as both an energy source and a carbon source.
E) H2S as an energy source and CO2 as a carbon source.
75) Which of the following statements is not true?
A) Archaea and bacteria have different membrane lipids.
B) Both archaea and bacteria generally lack membrane-enclosed organelles.
C) The cell walls of archaea lack peptidoglycan.
D) Only bacteria have histones associated with DNA.
E) Only some archaea use CO2 to oxidize H2, releasing methane.
76) Which of the following involves metabolic cooperation among prokaryotic cells?
A) binary fission
B) endospore formation
C) endotoxin release
D) biofilms
E) photoautotrophy
77) Bacteria perform each of the following ecological roles. Which role typically does not involve a
symbiosis?
A) skin commensalist
B) decomposer
C) aggregates with methane-consuming archaea
D) gut mutualist
E) pathogen
78) Plantlike photosynthesis that releases O2 occurs in
A) cyanobacteria.
B) chlamydias.
C) archaea.
D) actinomycetes.
E) chemoautotrophic bacteria.
