32) Bacteria able to perform the NH4+ + NO2– → N2 + 2H2O reaction have been discovered in
laboratory bioreactors and wastewater treatment systems. Researchers predicted that these
bacteria should exist in oceans. They measured the concentration of NH4+, NO2–, NO3–, and O2
in the Black Sea as a function of water depth (M. Kuypers et al. 2003 Anaerobic ammonium
oxidation by anammox bacteria in the Black Sea. Nature 422:608-11) to determine where in the
sea the bacteria might live. Analyzing data presented in the figure above, at what depth would
you expect to find the bacteria? (Note: In the figure, different scales are used to show
concentrations of NH4+, NO2–, NO3–, and O2.)
A) in the top 50 meters
B) at a depth of 75 meters
C) at a depth of 92 meters
D) below 100 meters
15
33) 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 oxygen (O2) enters heterocysts during hours of peak photosynthesis to have a
somewhat-inhibitory effect on nitrogen fixation.
B) Atmospheric nitrogen (N2) levels increase at night because plants are no longer metabolizing
this gas, so they are not absorbing this gas through their stomata.
C) Heterocyst walls become less permeable to nitrogen (N2) influx during darkness.
D) 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).
Use the information in the following paragraph to answer the question(s) below.
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.
34) This bacterium derives nutrition by digesting human intestinal contents. Thus, this bacterium
is an _____.
A) aerobic chemoheterotroph
B) aerobic chemoautotroph
C) anaerobic chemoheterotroph
Use the following information to answer the question(s) below.
Nitrogenase, the enzyme that catalyzes nitrogen fixation, is inhibited whenever free oxygen (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.”
35) 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) 3 and 4
36) Think about this description of the colonial aquatic cyanobacterium, Anabaena. What two
questions below are important for understanding how nitrogen (N2) enters heterocysts, and how
oxygen (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 photosynthetic cells are permeable to O2 and carbon dioxide
(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 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 Anabaena 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) 4 and 6
17
The following table depicts characteristics of five prokaryotic species (A-E). Use the information
in the table to answer the question(s) below
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
37) 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
18
Use the following information to answer the question(s) below.
For several decades now, amphibian species worldwide have been in decline. A significant
proportion of the decline seems to be due to the spread of the chytrid fungus, Batrachochytrium
dendrobatidis (Bd). Chytrid sporangia reside within the epidermal cells of infected animals,
animals that consequently show areas of sloughed skin. They can also be lethargic, which is
expressed through failure to hide and failure to flee. The infection cycle typically takes four to
five days, at the end of which zoospores are released from sporangia into the environment. In
some amphibian species, mortality rates approach 100%; other species seem able to survive the
infection.
38) If infection primarily involves the outermost layers of adult amphibian skin, and if the
chytrids use the skin as their sole source of nutrition, then which term best applies to the
chytrids?
A) anaerobic chemoautotroph
B) aerobic chemoautotroph
C) anaerobic chemoheterotroph
39) While examining a rock surface, you have discovered an interesting new organism. Which of
the following criteria will allow you to classify the organism as belonging to Bacteria but not
Archaea or Eukarya?
A) Cell walls are made primarily of peptidoglycan.
B) The organism does not have nucleus.
C) The lipids in its plasma membrane consist of glycerol bonded to straight-chain fatty acids.
D) It can survive at a temperature over 100°C.
40) Which of the following describe all existing bacteria?
A) pathogenic, omnipresent, morphologically diverse
B) extremophiles, tiny, abundant
C) tiny, ubiquitous, metabolically diverse
D) morphologically diverse, metabolically diverse, extremophiles
19
41) You have found a new prokaryote. What line of evidence would support your hypothesis that
the organism is a cyanobacterium?
A) It is able to form colonies and produce oxygen.
B) It is an endosymbiont.
C) It forms chains called mycelia.
42) Which statement about the domain Archaea is true?
A) Genetic prospecting has recently revealed the existence of many previously unknown
archaean species.
B) The genomes of archaeans are unique, containing no genes that originated within bacteria.
C) No archaeans can inhabit solutions that are nearly 30% salt.
D) No archaeans are adapted to waters with temperatures above the boiling point.
43) Which of the following traits do archaeans and bacteria share?
A) composition of the cell wall
B) composition of the cell wall and lack of a nuclear envelope
C) lack of a nuclear envelope and presence of plasma membrane
D) presence of plasma membrane and composition of the cell wall
44) Assuming that each of these possesses a cell wall, which prokaryotes should be expected to
be most strongly resistant to plasmolysis in hypertonic environments?
A) extreme halophiles
B) extreme thermophiles
C) methanogens
D) cyanobacteria
45) The thermoacidophile Sulfolobus acidocaldarius lacks peptidoglycan, but still possesses a
cell wall. What is likely to be true of this species?
1. It is a bacterium.
2. It is an archaean.
3. The optimal pH of its enzymes will lie above pH 7.
4. The optimal pH of its enzymes will lie below pH 7.
5. It could inhabit certain hydrothermal springs.
6. It could inhabit alkaline hot springs.
A) 1, 3, and 6
B) 2, 4, and 5
C) 1, 3, and 5
46) A fish that has been salt-cured subsequently develops a reddish color. You suspect that the
fish has been contaminated by the extreme halophile Halobacterium. Which of these features of
cells removed from the surface of the fish, if confirmed, would support your suspicion?
1. the presence of the same photosynthetic pigments found in cyanobacteria
2. cell walls that lack peptidoglycan
3. cells that are isotonic to conditions on the surface of the fish
4. cells unable to survive salt concentrations lower than 9%
5. the presence of very large numbers of ion pumps in its plasma membrane
A) 2 and 5
B) 3 and 4
C) 1, 4, and 5
D) 2, 3, 4, and 5
21
The following table depicts characteristics of five prokaryotic species (A-E). Use the information
in the table to answer the question(s) below
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
47) Which species is most likely to be found in sewage treatment plants and in the guts of cattle?
A) species A
B) species B
C) species C
D) species D
48) Which of the following extremophiles might researchers most likely use as a model for the
earliest organisms on Earth?
A) a bacterium found on another planet or moon
B) an archaean capable of surviving in the polar ice caps
C) an anaerobic archaean species
22
49) Mitochondria are thought to be the descendants of certain alpha proteobacteria. They are,
however, no longer able to lead independent lives because most genes originally present on their
chromosomes have moved to the nuclear genome. Which phenomenon accounts for the
movement of these genes?
A) plasmolysis
B) conjugation
C) translation
D) horizontal gene transfer
Use the following information to answer the question(s) below.
The most recently discovered phylum in the animal kingdom (1995) is the phylum Cycliophora.
It includes three species of tiny organisms that live in large numbers on the outsides of the
mouthparts and appendages of lobsters. The feeding stage permanently attaches to the lobster via
an adhesive disk and collects scraps of food from its host’s feeding by capturing the scraps in a
current created by a ring of cilia. The body is sac-like and has a U-shaped intestine that brings
the anus close to the mouth. Cycliophorans are coelomates, do not molt (though their host does),
and their embryos undergo spiral cleavage.
50) If harboring large populations of cycliophorans neither helps nor harms their lobster hosts,
then cycliophorans can be properly considered to be _____.
1. parasites
2. mutualists
3. commensals
4. symbionts
5. endosymbionts
A) 1 and 4
B) 3 and 4
C) 2 and 5
D) 3 and 5
51) Bacteria perform each of the following ecological roles. Which role typically does NOT
involve symbiosis?
A) skin commensalist
B) decomposer
C) aggregates with methane-consuming archaea
D) gut mutualist
Use the following information to answer the question(s) below.
Healthy individuals of Paramecium bursaria contain photosynthetic algal endosymbionts of the
genus Chlorella. When within their hosts, the algae are referred to as zoochlorellae. In aquaria
with light coming from only one side, P. bursaria gather at the well-lit side, whereas other
species of Paramecium gather at the opposite side. The zoochlorellae provide their hosts with
glucose and oxygen, and P. bursaria provides its zoochlorellae with protection and motility. P.
bursaria can lose its zoochlorellae in two ways: (1) if kept in darkness, the algae will die; and (2)
if prey items (mostly bacteria) are absent from its habitat, P. bursaria will digest its
zoochlorellae.
52) A P. bursaria cell that has lost its zoochlorellae is aposymbiotic. If aposymbiotic cells have
population growth rates the same as those of healthy, zoochlorella-containing P. bursaria in
well-lit environments with plenty of prey items, then such an observation would be consistent
with which type of relationship?
A) parasitic
B) commensalistic
C) toxic
D) mutualistic
53) The termite gut protist Mixotricha paradoxa has at least two kinds of bacteria attached to its
outer surface. One kind is a spirochete that propels its host through the termite gut. A second
type of bacteria synthesizes adenosine triphosphate (ATP), some of which is used by the
spirochetes. The locomotion provided by the spirochetes introduces the ATP-producing bacteria
to new food sources. Which term(s) is (are) applicable to the relationship between the two kinds
of bacteria?
1. mutualism
2. parasitism
3. symbiosis
4. metabolic cooperation
A) 1 and 2
B) 2 and 3
C) 1, 3, and 4
D) 2, 3, and 4
24
54) If all prokaryotes on Earth suddenly vanished, which of the following would be the most
likely and most direct result?
A) Human populations would thrive in the absence of disease.
B) Bacteriophage numbers would dramatically increase.
C) The recycling of nutrients would be greatly reduced, at least initially.
D) There would be no more pathogens on Earth.
55) In a hypothetical situation, a bacterium lives on the surface of a leaf, where it obtains
nutrition from the leaf’s nonliving, waxy covering while inhibiting the growth of other microbes
that are plant pathogens. If this bacterium gains access to the inside of a leaf, however, it causes
a fatal disease in the plant. Once the plant dies, the bacterium and its offspring decompose the
plant. What is the correct sequence of ecological roles played by the bacterium in the situation
described here?
1. nutrient recycler
2. mutualist
3. commensal
4. pathogen
5. primary producer
A) 1, 3, 4
B) 2, 3, 4
C) 2, 4, 1
D) 1, 2, 5
56) What is the goal of bioremediation?
A) to improve human health with the help of living organisms such as bacteria
B) to clean up areas polluted with toxic compounds by using bacteria
C) to improve soil quality for plant growth by using bacteria
D) to improve bacteria for production of useful chemicals
25
57) Foods can be preserved in many ways by slowing or preventing bacterial growth. Which of
these methods should be LEAST effective at inhibiting bacterial growth?
A) Refrigeration: slows bacterial metabolism and growth.
B) Closing previously opened containers: prevents more bacteria from entering, and excludes
oxygen.
C) Pickling: creates a pH at which most bacterial enzymes cannot function.
D) Canning in heavy sugar syrup: creates osmotic conditions that remove water from most
58) Broad-spectrum antibiotics inhibit the growth of most intestinal bacteria. Consequently,
assuming that nothing is done to counter the reduction of intestinal bacteria, a hospital patient
who is receiving broad-spectrum antibiotics is most likely to become _____.
A) unable to fix carbon dioxide
B) antibiotic resistant
C) unable to synthesize peptidoglycan
D) deficient in certain vitamins and nutrients
59) The pathogenic prokaryotes that cause cholera are _____.
A) archaea that release an exotoxin
B) archaea that release an endotoxin
C) bacteria that release an exotoxin
D) bacteria that release an endotoxin
60) The soil layer surrounding plant roots, called the rhizosphere, has been shown in some cases
to _____.
A) contain fungi that produce an endotoxin which inhibits the growth rhizomes
B) inhibit the growth of fungal pathogens
C) produce vitamins essential for the uptake of nitrogen
D) contain archaea which produce antibiotics that prevent the growth of most bacteria
26
61) When a virus infects a bacterial cell, often new viruses are assembled and released when the
host bacterial cell is lysed. If these new viruses go on to infect new bacterial cells the host cells
may not be lysed. What is the most plausible explanation for this?
A) The bacterial cell must be resistant to infection by the virus.
B) The virus carries genes that confer resistance to the host bacterial cell.
C) The host bacterium couples the viral infection with transformation.
62) Sexual reproduction in eukaryotes increases genetic variation. In prokaryotes,
transformation, transduction, and conjugation are mechanisms that increase genetic variation. A
fundamental difference between the generations of genetic variation in the two domains is:
A) Eukaryotes are able to generate mutations in response to environmental stress while
prokaryotes only generate random variation.
B) Eukaryotic variation occurs primarily within a single generation while prokaryotic variation
occurs over many generations.
C) Crossing over is a major mechanism in creating genetic variation in prokaryotes while
independent assortment is a major mechanism is eukaryotes.
D) Eukaryotic genetic variation occurs with vertical gene transfer while prokaryotic genetic
63) In prokaryotes new mutations accumulate quickly in populations, while in eukaryotes new
mutations accumulate much more slowly. The primary reasons for this are
A) Prokaryotes have short generation times and large population sizes.
B) Prokaryotes have random mutations while eukaryotes can target genes for mutations; thus
mutations may not accumulate as quickly in eukaryotes but they are more useful to the organism.
C) The DNA in prokaryotes is not as stable as eukaryotic DNA and is thus more likely to mutate.
D) Prokaryote mutations are less effective than eukaryote mutations in providing variation for
evolution.