50) Which tree depicts the closest relationship between zygomycetes and chytrids?
A) I
B) II
C) III
D) IV
51) Which tree depicts the microsporidians as a sister group of the fungi, rather than as a fungus?
A) I
B) II
C) III
D) IV
The following figure depicts the outline of a large fairy ring that has appeared overnight in an open
meadow, as viewed from above. The fairy ring represents the furthest advance of this mycelium through
the soil. Locations A D are all 0.5 meters below the soil surface. Responses may be used once, more
than once, or not at all.
52) What is the most probable location of the oldest portion of this mycelium?
A) A
B) B
C) C
D) D
53) Which location is nearest to basidiocarps?
A) A
B) B
C) C
D) D
54) At which location is the mycelium currently absorbing the most nutrients per unit surface area, per
unit time?
A) A
B) B
C) C
D) D
55) At which location should one find the lowest concentration of fungal enzymes, assuming that the
enzymes do not diffuse far from their source, and that no other fungi are present in this habitat?
A) A
B) B
C) C
D) D
56) Assume that all four locations are 0.5 m above the surface. On a breezy day with prevailing winds
blowing from left to right, where should one expect to find the highest concentration of free
basidiospores in an air sample?
A) A
B) B
C) C
D) D
57) In which of the following human mycoses should one expect to find a growth pattern most similar to
that of the mycelium that produced the fairy ring?
A) skin mycoses
B) coccidiomycosis (lung infection)
C) systemic (bloodborne) Candida infection
D) Sporothrix infection of lymphatic vessels
E) Tinea tonsurans infection limited to interior of hair shafts
58) If the fungus that produced the fairy ring can also produce arbuscules, then which of the following is
most likely to be buried at location “C”?
A) septic tank
B) tree stump
C) deceased animal
D) fire pit
E) cement-capped well
Scenario Questions
Please refer to the following information to answer the next few questions.
Diploid nuclei of the ascomycete, Neurospora crassa, contain 14 chromosomes. A single diploid cell in
an ascus will undergo one round of meiosis, followed in each of the daughter cells by one round of
mitosis, producing a total of eight ascospores.
59) If a single, diploid G2 nucleus in an ascus contains 400 nanograms (ng) of DNA, then a single
ascospore nucleus of this species should contain how much DNA (ng), carried on how many
chromosomes?
A) 100, carried on 7 chromosomes
B) 100, carried on 14 chromosomes
C) 200, carried on 7 chromosomes
D) 200, carried on 14 chromosomes
E) 400, carried on 14 chromosomes
60) What is the ploidy of a single mature ascospore?
A) monoploid
B) diploid
C) triploid
D) tetraploid
E) polyploid
61) Each of the eight ascospores present at the end of mitosis has the same chromosome number and
DNA content (ng) as each of the four cells at the end of meiosis. What must have occurred in each spore
between the round of meiosis and the round of mitosis?
A) double fertilization
B) crossing over
C) nondisjunction
D) autopolyploidy
E) S phase
Unicellular yeasts can be represented as spheres, whereas filamentous hyphae more closely resemble
cylinders. As these two geometric figures increase in size, their surface area–to-volume ratios change.
The following tables demonstrate how this ratio changes, first for spheres, and second for cylinders. For
the cylinder, girth (i.e., radius, r) will remain constant, whereas length, L, will increase. Note the
formulas below the respective tables.
A sphere’s change in surface area and volume with increasing radius, r
Radius
Surface Area
Volume
1
12.56
4.19
2
50.24
33.48
3
113.04
113.01
4
200.96
267.87
5
314.0
523.0
Area of a Sphere = 4r2 Volume of a Sphere = 4/3r3
A cylinder’s change in surface area and volume with increasing length, L
Radius
Surface Area
Volume
1
12.56
3.14
2
37.68
6.28
3
75.36
9.42
4
125.6
12.56
5
188.4
15.7
Area of a Cylinder = 2(r2) + 2rL Volume of a Cylinder = r2L
62) As a direct result of increasing surface area in both yeasts and filamentous hyphae, which cell
structures/materials must also increase?
1. amount of chitin
2. number of nuclei
3. amount of plasma membrane
4. number of mitochondria
5. amount of peptidoglycan
A) 1 only
B) 1 and 3
C) 2 and 3
D) 2 and 4
E) 1, 3, and 5
63) Which statement is a correct interpretation of the data in the previous tables?
A) As a sphere gets bigger, its surface area and volume increase at about the same pace.
B) As a cylinder gets bigger, its surface area increases at a greater pace than does its volume.
C) As a cylinder gets bigger, its volume increases at about the same pace at which the volume of a
sphere increases.
D) As spheres and cylinders get bigger, the surface area of a cylinder increases at a faster pace than does
the surface area of a sphere.
64) Both axes of the graph are linear. Thus, the shape of the line plotted on this graph most accurately
depicts the
A) volume of a sphere as the radius, r, increases.
B) surface area of a sphere as the radius, r, increases.
C) volume of a cylinder as length, L, increases.
D) surface area of a cylinder as length, L, increases.
65) Surface area represents the area available for exchange with the environment, whereas volume
represents the cytoplasm which requires nutrients and from which waste products (usually toxic) must
be removed. Which of the following should provide the most favorable conditions for effective
exchange?
A) a smaller unicellular yeast
B) a larger unicellular yeast
C) a shorter filamentous hypha
D) a longer filamentous hypha
66) Some fungi can exist either as unicellular yeasts or as filamentous hyphae. Which of these forms
would be most favorable in an environment where nutrients are limited?
A) a smaller unicellular yeast
B) a larger unicellular yeast
C) a shorter filamentous hypha
D) a longer filamentous hypha
Recent genetic studies of the structure of microsporidian genomes, as well as the sequences of their
tubulin genes and the gene for RNA polymerase II, indicate that microsporidians are closely related to
the fungi. Microsporidians lack flagella, centrioles, peroxisomes, and mitochondria (although they do
have degenerate mitochondria, called mitosomes). They have the smallest genome of any eukaryote, and
it is a genome that changes quickly. The genome is contained within two haploid nuclei. All
microsporidians are obligate intracellular parasites. They use a unique organelle called a polar filament
to gain access to the cells of their hosts. One species causes chronic diarrhea in AIDS patients. Another
parasitizes Anopheles gambiae, the mosquito that transmits a fatal form of malaria to humans.
67) Given the eukaryotic structures they lack, it should be expected that microsporidians also lack
A) the “9 + 2 pattern” of microtubules.
B) chitin.
C) lysosomes.
D) nuclei.
E) centrosomes.
68) The lifestyle of microsporidians is most similar to that of
A) scavengers.
B) viruses.
C) free-living yeasts.
D) ectoparasites.
69) Which of the following microsporidian features are shared with many other fungi?
1. chitinous cell wall
2. two haploid nuclei per cell
3. polar filament
4. chemoheterotrophy
A) 1 and 2
B) 1 and 3
C) 1 and 4
D) 1, 2, and 4
E) 2, 3, and 4
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.
70) Apart from direct amphibian-to-amphibian contact, what is the most likely means by which the
zoospores spread from one free-living amphibian to another?
A) by wind-blown spores
B) by flagella
C) by cilia
D) by pseudopods
E) by hyphae
71) The chytrid sporangia reside within the amphibian epidermal cells. Consequently, which term(s)
apply to Bd?
1. ectosymbionts
2. parasites
3. commensals
4. pathogens
5. endosymbionts
A) 1 and 2
B) 1 and 3
C) 2 and 4
D) 2, 3, and 5
E) 2, 4, and 5
72) Which of the following are protists, the organisms thought to share the closest ancestor with the
chytrids?
A) nucleariids
B) choanoflagellates
C) zygomycetes
D) algae
E) diplomonads
73) Sexual reproduction has not been observed in Bd. A Bd sporangium initially contains a single,
haploid cell. Which of the following processes must be involved in generating the multiple zoospores
eventually produced by each sporangium?
1. S phase
2. cytokinesis
3. mitosis
4. meiosis
A) 1 and 2
B) 1 and 3
C) 2 and 3
D) 1, 2, and 3
E) 1, 2, and 4
74) Sexual reproduction has not been observed in Bd. If its morphology and genetics did not identify it
as a chytridiomycete, then to which fungal group would Bd be assigned?
A) ascomycetes
B) zygomycetes
C) glomeromycetes
D) basidiomycetes
E) deuteromycetes
75) 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
D) aerobic chemoheterotroph
76) If Bd cannot grow properly at temperatures above 28°C (82°F), then, assuming the amphibians can
survive, in which time or place should the chytrid infection proceed most rapidly?
1. cooler months
2. warmer months
3. lower altitudes
4. higher altitudes
A) 1 or 3
B) 1 or 4
C) 2 or 3
D) 2 or 4
77) What makes it risky to rely on the presence of chitin in adult amphibian skin as the sole positive test
for the presence of chytrids?
A) Other mycoses may be in progress in the same amphibian simultaneously.
B) The amphibian may harbor arthropod ectoparasites simultaneously.
C) Bacterial infections may be simultaneously underway in the amphibian.
D) Three of the responses above are correct.
E) Two of the responses above are correct.
78) The fact that infection by Bd causes lethargy in many infected amphibians can have what effect on
efforts to accurately census the numbers of dead or dying amphibians at a particular time, in a particular
habitat?
A) It can cause underestimation, due to infected amphibians preferring to seek out refuges relative to
uninfected amphibians.
B) It can cause underestimation, due to increased predation on, and removal of, infected amphibians
relative to uninfected amphibians.
C) It can cause overestimation, because infected frogs should be more readily observable to human
census-takers than should uninfected amphibians.
D) All three of the above statements are plausible.
E) Two of the above statements are plausible.
79) When adult amphibian skin harbors populations of the bacterium, Janthinobacterium lividum (Jl),
chytrid infection seems to be inhibited. Which of the following represents the best experimental design
for conclusively determining whether this inhibition is real?
A) Inoculate uninfected amphibians with Jl, and determine whether the amphibians continue to remain
uninfected by chytrids.
B) Inoculate infected amphibians with Jl, and determine whether the amphibians recover from infection
by chytrids.
C) Take infected amphibians and assign them to two populations. Leave one population alone; inoculate
the other with Jl. Measure the rate at which infection proceeds in both populations.
D) Take infected amphibians and assign them to two populations. Inoculate one population with a high
dose of Jl; inoculate the other with a low dose of Jl. Measure the survival frequency in both populations.
80) A researcher took water in which a Jl population had been thriving, filtered the water to remove all
bacterial cells, and then applied the water to the skins of adult amphibians to see if there would
subsequently be a reduced infection rate by Bd when frog skins were inoculated with Bd. For which of
the following hypotheses is the procedure described a potential test?
A) the hypothesis that a toxin secreted by Jl cells kills Bd cells when both are present together on frog
skin
B) the hypothesis that Jl cells infect and kill Bd cells when both are present together on frog skin
C) the hypothesis that Jl outcompetes Bd when both are present together on a frog’s skin
D) the hypothesis that the presence of Jl on frog skin causes a skin reaction that prevents attachment by
Bd cells
Rose-picker’s disease is caused by the yeast, Sporothrix schenkii. The yeast grows on the exteriors of
rose-bush thorns. If a human gets pricked by such a thorn, the yeasts can be introduced under the skin.
The yeasts then assume a hyphal morphology and grow along the interiors of lymphatic vessels until
they reach a lymph node. This often results in the accumulation of pus in the lymph node, which
subsequently ulcerates through the skin surface and then drains.
81) The answer to which of these questions would be of most assistance to one who is attempting to
assign the genus Sporothrix to the correct fungal phylum?
A) Do these yeasts perform fermentation while growing on the rose-bush thorns, or do they wait until
inside a human host?
B) Does S. schenkii rely on animal infection to complete some part of its life cycle, or is the infection
merely opportunistic?
C) Are the hyphae in lymphatic vessels septate, or are they coenocytic?
D) Is S. schenkii best described as a decomposer, parasite, pathogen, or mutualist of humans?
E) Being a yeast, does S. schenkii perform the process of budding?
82) Say S. schenkii had initially been classified as a deuteromycete. Asci were later discovered in the
pus that oozed from an ulcerated lymph node, and the spores therein germinated, giving rise to S.
schenkii yeasts. Which two of these are conclusions that make sense on the basis of this information?
1. S. schenkii produces asexual spores within lymph nodes.
2. S. schenkii should be reclassified.
3. S. schenkii continues to have no known sexual stage.
4. The hyphae growing in lymphatic vessels probably belonged to a different fungal species.
5. S. schenkii yeasts belonging to two different mating strains were introduced by the same thorn prick.
A) 1 and 3
B) 1 and 5
C) 2 and 3
D) 2 and 5
E) 4 and 5
83) Humans have immune systems in which lymph nodes are important, because many phagocytes and
lymphocytes reside there. Given that a successful infection by S. schenkii damages lymph nodes
themselves, which of the following is most probable?
A) The hyphae secrete antibiotics, which increases the ability of the infected human to tolerate the
fungus.
B) Their conversion from yeast to hyphal morphology allows such fast growth that the body’s defenses
are at least temporarily overwhelmed.
C) Defensive cells of humans cannot detect foreign cells that are covered with cell walls composed of
cellulose.
D) Given that most fungal pathogens attack plants, human defenses are simply not adapted to seek out
and destroy fungi.
E) Given that most fungal pathogens of humans infect only the skin, human defenses are not adapted to
seek out and destroy systemic fungal infections.
End-of-Chapter Questions
The following questions are from the end-of–chapter “Test Your Understanding” section in Chapter 31
of the textbook.
84) All fungi share which of the following characteristics?
A) symbiotic
B) heterotrophic
C) flagellated
D) pathogenic
E) act as decomposers
85) Which feature seen in chytrids supports the hypothesis that they diverged earliest in fungal
evolution?
A) the absence of chitin within the cell wall
B) coenocytic hyphae
C) flagellated spores
D) formation of resistant zygosporangia
E) parasitic lifestyle
86) Which of the following cells or structures are associated with asexual reproduction in fungi?
A) ascospores
B) basidiospores
C) zygosporangia
D) conidiophores
E) ascocarps
87) The photosynthetic symbiont of a lichen is often
A) a moss.
B) a green alga.
C) a brown alga.
D) an ascomycete.
E) a small vascular plant.
88) Among the organisms listed here, which are thought to be the closest relatives of fungi?
A) animals
B) vascular plants
C) mosses
D) brown algae
E) slime molds
89) The adaptive advantage associated with the filamentous nature of fungal mycelia is primarily related
to
A) the ability to form haustoria and parasitize other organisms.
B) avoiding sexual reproduction until the environment changes.
C) the potential to inhabit almost all terrestrial habitats.
D) the increased probability of contact between different mating types.
E) an extensive surface area well suited for invasive growth and absorptive nutrition.