BY124 Ch. 31

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. 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

1 and 3

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

1 or 4

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

1, 2, and 3

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. 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?

100, carried on 7 chromosomes

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.

2 and 5

Plasmogamy can directly result in which of the following? 1. cells with a single haploid nucleus 2. heterokaryotic cells 3. dikaryotic cells 4. cells with two diploid nuclei

2 or 3

Which of the following microsporidian features are shared with many other fungi? 1. chitinous cell wall 2. haploid nuclei per cell 3. polar filament 4. chemoheterotrphy

2, 3, and 4

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

2, 4, 5

Arrange the following from largest to smallest: 1. ascospore 2. ascocarp 3. ascomycete 4. ascus

3, 2, 4, 1

Arrange the following from largest to smallest, assuming that they all come from the same fungus: 1. basidiocarp 2. basidium 3. basidiospore 4. mycelium 5. gill

4, 1, 5, 2, 3

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 AD are all 0.5 meters below the soil surface. Responses may be used once, more than once, or not at all. At which location is the mycelium currently absorbing the most nutrients per unit surface area, per unit time?

A

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 AD are all 0.5 meters below the soil surface. Responses may be used once, more than once, or not at all. 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

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 AD are all 0.5 meters below the soil surface. Responses may be used once, more than once, or not at all. Which location is nearest to basidiocarps?

A

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 AD are all 0.5 meters below the soil surface. Responses may be used once, more than once, or not at all. 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"?

B

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 AD are all 0.5 meters below the soil surface. Responses may be used once, more than once, or not at all. What is the most probable location of the oldest portion of this mycelium?

C

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 AD are all 0.5 meters below the soil surface. Responses may be used once, more than once, or not at all. 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?

D

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 AD are all 0.5 meters below the soil surface. Responses may be used once, more than once, or not at all. 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?

D

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. 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?

Does S. schenkii rely on animal infection to complete some part of its life cycle, or is the infection merely opportunistic?

Which tree depicts the microsporidians as a sister group of the ascomycetes?

I

Which tree depicts the closest relationship between zygomycetes and chytrids?

III

Which tree depicts the microsporidians as a sister group of the fungi, rather than as a fungus?

IV

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?

S phase

The photosynthetic symbiont of a lichen is most often

a green alga

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 longer filamentous hypha

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 longer filamentous hypha

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 chytrids?

aerobic chemoheterotroph

The adaptive advantage associated with the filamentous nature of fungal mycelia is primarily related to

an extensive surface area well suited for invasive growth and absorptive nutrition

Among the organisms listed here, which are thought to be the closest relatives of fungi?

animals

Chemicals, secreted by soil fungi, that inhibit the growth of bacteria are known as

antibiotics

Which description does not apply equally well to both sexual and asexual spores?

are produced by meiosis

Which statement is a correct interpretation of the data in the previous tables?

as a cylinder gets bigger, its surface area increases at a greater pace than does its volume

You are given an organism to identify. It has a fruiting body that contains many structures with eight haploid spores lines up in a row. What kind of fungus is this?

ascomycete

Among sac fungi, which of these correctly distinguishes ascospores from conidia?

ascospores have undergone genetic recombination during their production, whereas conidia have not

What are the sporangia of the bread mold Rhizopus?m

asexual structures that produce haploid spores

The multicellular condition of animals and fungi seems to have arisen

by convergent evolution

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. 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?

by flagella

Orchid seeds are tiny, with virtually no endosperm and with miniscule cotyledons. If such seeds are deposited in a dark, moist environment, then which of the following represents the most likely means by which fungi might assist in seed germination, given what the seeds lack?

by providing the embryos with some of the organic nutrients they have absorbed

Both fungus-farming ants and their fungi can synthesize the same structural polysaccharide from the beta-glucose. What is this polysaccharide?

chitin

Fossil fungi date back to the origin and early evolution of plants. What combination of environmental and morphological change is similar in the evolution of both fungi and plants?

colonization of land and loss of flagellated cells

The vegetative (nutritionally active) bodies of most fungi are

composed of hyphae, referred to as mycelium, usually underground

In what structures do both Penicillium and Aspergillus produce asexual spores?

conidiophores

Which of the following cells or structures are associated with asexual reproduction in fungi?

conidiophores

A fungal spore germinates, giving rise to a mycelium that grows outward into the soil surrounding the site where the spores originally landed. Which of the following accounts for the fungal movement, as described here?

cytoplasmic streaming in the hyphae

If all of their nuclei are equally active transcriptionally, then the cells of both dikaryotic and heterokaryotic fungi, in terms of gene products they can make, are essentially

diploid

Immediately after karyogamy occurs, which term applies?

diploid

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?

dueteromycetes

Which of the following terms refers to symbiotic relationships that involve fungi living between the cells in plant leaves?

endophytes

Which of the following conditions is caused by a fungus that is accidentally consumed along with rye flour?

ergotism

Which feature seen in chytrids supports the hypothesis that they diverged earliest in fungal evolution?

flagellated spores

When a mycelium infiltrates an unexploited source of dead organic matter, what are most likely to appear within the food source soon thereafter?

fungal enzymes

Which pathogenic fungi are found growing on the roots of grape vines, grape farmers sometimes respond by covering the ground around their vines with plastic sheeting and pumping gaseous fungicide into the soil. The most important concern of grape farmers who engage in this practice should be that the

fungicide might also kill mycorrhizae

The functional significance of porous septa in certain fungal hyphae is most similar to that represented by which pair of structures in animal cells and plant cells, respectively?

gap junctions - plasmodesmata

Which of these paired fungal structures are structurally and functionally most alike?

haustoria and arbuscules

All fungi share which of the following characteristics?

heterotrophic

If Penicillium typically secretes penicillin without disturbing the lichen relationship in which it is engaged, then what must have been true about its partner?

it should have lacked peptidoglycan in its cell wall

Asexual reproduction in yeasts occurs by budding. Due to unequal cytokinesis, the "bud" cell receives less cytoplasm than the parent cell. Which of the following should be true of the smaller cell unit it reaches the size of the larger cell?

it should produce fewer fermentation products per unit time

Which process occurs in fungi and has the opposite effect on a cell's chromosome number than does meiosis I?

karyogamy

Mycorrhizae are to the roots of vascular plants as endophytes are to vascular plants'

leaf mesophyll

Consider two hyphae having equal dimensions: one from septate species and the other from coenocytic species. Compared with the septate species, the coenocytic species should have

less chitin

Which of the following has the least affiliation with all of the others?

lichens

If haustoria from the fungal partner were to appear within the photosynthetic partner of a lichen, and if the growth rate of the photosynthetic partner consequently slowed substantially, then this would support the claim that

lichens are not purely mutualistic relationships

What is the ploidy of a single mature ascospore?

monoploid

Which of the following are protists, the organism thought to share the closest ancestor with the chytrids?

nucleariids

Which of the following characteristics is shared by both chytrids and other kinds of fungi?

nucleotide sequences of several genes

Which of the following best describes the physical relationship of the partners involved in lichens?

photosynthetic cells are surrounded by fungal hyphae

In septate fungi, what structures allow cytoplasmic streaming to distribute needed nutrients, synthesized compounds, and organelles throughout the hyphae?

pores in cross-walls

If all fungi in an environment that perform decomposition were to suddenly die, then which group of organisms should benefit most, due to the fact that their fungal competitors have been removed?

prokaryotes

Both fungus-derived antibiotics and hallucinogens used by humans probably evolved in fungi as a means to

reduce competition for nutrients

In most fungi, karyogamy does not immediately follow plasmogamy, which consequently

results in heterokaryotic or dikaryotic cells

What accounts most directly for the extremely fast growth of a fugal mycelium?

rrapid distribution of synthesized proteins by cytoplasmic streaming

After cytokinesis occurs in budding yeasts, the daughter cell has a

similar nucleus and less cytoplasm than the mother cell

A billionaire buys a sterile volcanic island that recently emerged from the sea. To speed the arrival of conditions necessary for plant growth, the billionaire might be advised to aerially sow what over the island?

soredia

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?

take infected amphibians and assign them to two populations. Leave one population alone; inoculate the other with JI. Measure the rate at which infection proceeds in both populations

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 `Given the eukaryotic structures they lack, it should be expected that microsporidians also lack

the "9+2 pattern" of microtubules

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?

the hypothesis that a toxins secreted by JI cells kills Bd cells when both are present together on frog skin

Many infected animals are induced by the parasitic microsporidians to develop huge cells, known as zenomas, which are full of spores. Given their large size, what should be true of the xenomas?

the parasite must endow the zenoma with some way to overcome its unfavorable surface area-to-volume ratio

What do fungi arthropods have in common?

the protective coats of both groups are made of chitin

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 possible?

their conversion from yeast to hyphal morphology allows such fast growth that the body's defenses are at least temporarily overwhelmed

Sexual reproduction has never been observed among the fungi that produce the blue-green marbling of blue cheeses. What is true of these fungi and others that do not have a sexual stage?

their spores are probably produced by mitosis

Which of the following is a characteristic of hyphate fungi (fungi featuring hyphae)?

they are adapted for rapid directional growth to new food sources

Which of the following statements is true of deuteromycetes?

they are the group of fungi that have, at present, no known sexual stage

The microsporidian, Brachiola gambiae, parasitizes the mosquito, Anopheles gambiae. Adult female mosquitoes must take blood meals in order for their eggs to develop, and it is while they take blood that they transmit malarial parasites to humans. Male mosquitoes drink flower nectar. If humans are to safely and effectively use Brachiola gambiae as a biological control to reduce human deaths from malaria, then how many of the following statements should be true? 1. Brachiola should kill the mosquitoes before the malarial parasite they carry reaches maturity. 2. The microsporidian should not be harmful to other insects. 3. Microsporidians should infect mosquito larvae, rather than mosquito adults. 4. The subsequent decline in anopheline mosquitoes should not significantly disrupt human food resources or other food webs. 5. Brachiola must be harmful to male mosquitoes, but not to female mosquitoes.

three statements

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?

two of the above statements are plausible

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?

two of the responses are correct

Lichens are symbiotic associations of fungi and

two of these responses are correct

The hydrolytic digestion of which of the following should produce monomers that are animated molecules of beta-glucose?

two of these responses are correct

The lifestyle of microsporidians is most similar to that of

viruses

Both axes of the graph are linear. Thus, the shape of the line plotted on this graph most accurately depicts the

volume of a cylinder as length, L, increases

In both lichens and mycorrhizae, what does the fungal partner provide to its photosynthetic partner?

water and minerals