24.E: Fungi (Exercises)
24.1: Characteristics of Fungi
Review Questions
Which polysaccharide is usually found in the cell wall of fungi?
- starch
- glycogen
- chitin
- cellulose
- Answer
-
C
Which of these organelles is not found in a fungal cell?
- chloroplast
- nucleus
- mitochondrion
- Golgi apparatus
- Answer
-
A
The wall dividing individual cells in a fungal filament is called a
- thallus
- hypha
- mycelium
- septum
- Answer
-
D
During sexual reproduction, a homothallic mycelium contains
- all septated hyphae
- all haploid nuclei
- both mating types
- none of the above
- Answer
-
C
Free Response
What are the evolutionary advantages for an organism to reproduce both asexually and sexually?
- Answer
-
Asexual reproduction is fast and best under favorable conditions. Sexual reproduction allows the recombination of genetic traits and increases the odds of developing new adaptations better suited to a changed environment.
Compare plants, animals, and fungi, considering these components: cell wall, chloroplasts, plasma membrane, food source, and polysaccharide storage. Be sure to indicate fungi’s similarities and differences to plants and animals.
- Answer
-
Animals have no cell walls; fungi have cell walls containing chitin; plants have cell walls containing cellulose. Chloroplasts are absent in both animals and fungi but are present in plants. Animal plasma membranes are stabilized with cholesterol, while fungi plasma membranes are stabilized with ergosterol, and plant plasma membranes are stabilized with phytosterols. Animals obtain N and C from food sources via internal digestion. Fungi obtain N and C from food sources via external digestion. Plants obtain organic N from the environment or through symbiotic N-fixing bacteria; they obtain C from photosynthesis. Animals and fungi store polysaccharides as glycogen, while plants store them as starch.
24.2: Classifications of Fungi
Review Questions
The most primitive phylum of fungi is the ________.
- Chytridiomycota
- Zygomycota
- Glomeromycota
- Ascomycota
- Answer
-
A
Members of which phylum produce a club-shaped structure that contains spores?
- Chytridiomycota
- Basidiomycota
- Glomeromycota
- Ascomycota
- Answer
-
B
Members of which phylum establish a successful symbiotic relationship with the roots of trees?
- Ascomycota
- Deuteromycota
- Basidiomycota
- Glomeromycota
- Answer
-
D
The fungi that do not reproduce sexually use to be classified as ________.
- Ascomycota
- Deuteromycota
- Basidiomycota
- Glomeromycota
- Answer
-
B
Free Response
What is the advantage for a basidiomycete to produce a showy and fleshy fruiting body?
- Answer
-
By ingesting spores and disseminating them in the environment as waste, animals act as agents of dispersal. The benefit to the fungus outweighs the cost of producing fleshy fruiting bodies.
For each of the four groups of perfect fungi (Chytridiomycota, Zygomycota, Ascomycota, and Basidiomycota), compare the body structure and features, and provide an example.
- Answer
-
Chytridiomycota (Chytrids) may have a unicellular or multicellular body structure; some are aquatic with motile spores with flagella; an example is the Allomyces . Zygomycota (conjugated fungi) have a multicellular body structure; features include zygospores and presence in soil; examples are bread and fruit molds. Ascomycota (sac fungi) may have unicellular or multicellular body structure; a feature is sexual spores in sacs (asci); examples include the yeasts used in bread, wine, and beer production. Basidiomycota (club fungi) have multicellular bodies; features includes sexual spores in the basidiocarp (mushroom) and that they are mostly decomposers; mushroom-producing fungi are an example.
24.3: Ecology of Fungi
Review Questions
What term describes the close association of a fungus with the root of a tree?
- a rhizoid
- a lichen
- a mycorrhiza
- an endophyte
- Answer
-
C
Why are fungi important decomposers?
- They produce many spores.
- They can grow in many different environments.
- They produce mycelia.
- They recycle carbon and inorganic minerals by the process of decomposition.
- Answer
-
D
Free Response
Why does protection from light actually benefit the photosynthetic partner in lichens?
- Answer
-
Protection from excess light that may bleach photosynthetic pigments allows the photosynthetic partner to survive in environments unfavorable to plants.
24.4: Fungal Parasites and Pathogens
Review Questions
A fungus that climbs up a tree reaching higher elevation to release its spores in the wind and does not receive any nutrients from the tree or contribute to the tree’s welfare is described as a ________.
- commensal
- mutualist
- parasite
- pathogen
- Answer
-
A
A fungal infection that affects nails and skin is classified as ________.
- systemic mycosis
- mycetismus
- superficial mycosis
- mycotoxicosis
- Answer
-
C
Free Response
Why can superficial mycoses in humans lead to bacterial infections?
- Answer
-
Dermatophytes that colonize skin break down the keratinized layer of dead cells that protects tissues from bacterial invasion. Once the integrity of the skin is breached, bacteria can enter the deeper layers of tissues and cause infections.
24.5: Importance of Fungi in Human Life
Review Questions
Yeast is a facultative anaerobe. This means that alcohol fermentation takes place only if:
- the temperature is close to 37°C
- the atmosphere does not contain oxygen
- sugar is provided to the cells
- light is provided to the cells
- Answer
-
B
The advantage of yeast cells over bacterial cells to express human proteins is that:
- yeast cells grow faster
- yeast cells are easier to manipulate genetically
- yeast cells are eukaryotic and modify proteins similarly to human cells
- yeast cells are easily lysed to purify the proteins
- Answer
-
C
Free Response
Historically, artisanal breads were produced by capturing wild yeasts from the air. Prior to the development of modern yeast strains, the production of artisanal breads was long and laborious because many batches of dough ended up being discarded. Can you explain this fact?
- Answer
-
The dough is often contaminated by toxic spores that float in the air. It was one of Louis Pasteur’s achievements to purify reliable strains of baker’s yeast to produce bread consistently.