Question 1

The following questions refer to the description below.
A lichen is a mutualistic association between a fungus and a green algae or cyanobacteria. There are clear morphological differences in lichen body form; some have flat bodies and are very close together, others have leaf-like bodies, and still others grow upright. The association between the two organisms is so complete that lichens are classified as a single organism.
-Lichens are found in a wide variety of habitats, including rocks, soil, tree bark, buildings, etc. Aging of lichens has shown that some are thousands of years old; how is this possible when you see that some of these lichens are very small?

Accepted Answer

Lichens can enter a dormant phase when resources such as water are limited, allowing them to grow very slowly and potentially live for thousands of years.

Question 2

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

Accepted Answer

Fungi and animals are both part of the Opisthokonta clade, sharing a more recent common ancestor with each other than with plants, algae, or slime molds.

Question 3

The following questions refer to the description below.
A lichen is a mutualistic association between a fungus and a green algae or cyanobacteria. There are clear morphological differences in lichen body form; some have flat bodies and are very close together, others have leaf-like bodies, and still others grow upright. The association between the two organisms is so complete that lichens are classified as a single organism.
-Biologists have noted that lichen structure differs substantially from the fungus component grown separately. What is the most plausible explanation for this?

Accepted Answer

The photosynthetic partners, either green algae or cyanobacteria, influence the lichen structure. The association between the two organisms is so complete that they are classified as a single organism.

Question 4

All fungi share which of the following characteristics?

Accepted Answer

The answer of All fungi share which of the following...

Question 5

When adult amphibian skin harbours 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?

Accepted Answer

This design includes a control group and allows for comparison between treated and untreated groups, providing clear evidence of Jl's effect on chytrid infection.

Question 6

The photosynthetic symbiont of a lichen is often

Accepted Answer

The photosynthetic symbiont in most lichens is a green alga, although in some cases it may be a cyanobacterium or both a green alga and a cyanobacterium. The fungal partner in the lichen is typically an ascomycete.

Question 7

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

Accepted Answer

The filamentous nature of fungal mycelia provides an extensive surface area that is well suited for invasive growth and absorptive nutrition. This enables fungi to efficiently extract nutrients from their environment, which is particularly important in nutrient-poor habitats. Additionally, the extensive surface area increases the probability of contact between different mating types, facilitating sexual reproduction. However, the filamentous nature of fungi does not necessarily provide an adaptive advantage for haustoria formation or parasitism, avoiding sexual reproduction, or inhabiting all terrestrial habitats.

Question 8

Use the following information to answer the questions below.
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.
-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.

Accepted Answer

The answer of Use the following information to answer the...

Question 9

Use the following information to answer the questions 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.
-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?

Accepted Answer

Chytrids are not able to produce their own food through photosynthesis, so they must obtain organic matter from another source. Since they obtain their energy from chemical reactions and require oxygen, they are best classified as aerobic chemoheterotrophs.

Question 10

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?

Accepted Answer

Both options A and B are correct. Other mycoses in progress in the same amphibian could interfere with the detection of chitin from chytrids, and the presence of arthropod ectoparasites could contribute to false positives for chitin detection. Option C is not directly related to the detection of chitin and chytrids, making option D incorrect.

Question 11

Use the following information to answer the questions below.
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?

Accepted Answer

The answer of Use the following information to answer the...

Question 12

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?

Accepted Answer

The procedure described tests the hypothesis that a toxin secreted by Jl cells kills Bd cells. Since the water was filtered to remove all bacterial cells, leaving only substances that could have been secreted by Jl, applying this water tests whether something from Jl (like a toxin) can reduce Bd infection without the physical presence of Jl cells.

Question 13

Use the following information to answer the questions 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.
-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

Accepted Answer

Bd (Batrachochytrium dendrobatidis), the fungus causing chytrid infection in amphibians, thrives in cooler temperatures and struggles at temperatures above 28°C. Cooler months and higher altitudes typically have lower temperatures, providing a more suitable environment for Bd to grow and infect amphibians.

Question 14

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?

Accepted Answer

A and B are plausible because lethargic, infected amphibians may hide or be more susceptible to predation, both of which could lead to underestimation of their numbers. C is not plausible because lethargy would likely make infected amphibians less observable, not more.

Question 15

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?

Accepted Answer

S. schenkii's conversion from yeast to hyphal morphology allows it to grow rapidly, overwhelming the immune system's defences and causing damage to lymph nodes. A, C, D, and E are incorrect because there is no evidence to support those statements about S. schenkii or the human immune system's ability to detect and respond to fungal infections.

Question 16

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

Accepted Answer

The presence of flagellated spores in chytrids is a unique feature that sets them apart from other fungi. This suggests that chytrids may have been the earliest diverging group in fungal evolution, as they evolved a primitive means of motility that was lost in later diverging lineages.

Question 17

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

Accepted Answer

Conidiophores are associated with asexual reproduction in fungi. They produce specialized cells called conidia, which can be dispersed and germinate into new fungal individuals. The other choices are associated with sexual reproduction in fungi.

Quiz 31: Fungi