Exam 2: ch. 29 Fungi

In septate fungi, what structures allow cytoplasmic streaming to distribute needed nutrients, synthesized compounds, and organelles throughout the hyphae? A) multiple chitinous layers in cross-walls B) pores in septa C) complex microtubular cytoskeletons D) two nuclei E) tight junctions that form in cross-walls between cells

B) pores in septa

All fungi are _____. A) symbiotic B) heterotrophic C) flagellated D) pathogenic E) decomposers

B) heterotrophic

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

Plasmogamy can directly result in (2) heterokaryotic cells or (3) dikaryotic cells.

Part C - Ecological interactions of fungi Most fungi are decomposers; they recycle the nutrients from nonliving organic matter. Other fungi are specialized to live in symbiotic relationships with other organisms. Some fungi live as parasites and others as mutualists. Most plants, in fact, could not survive and grow without their fungal partner. This table lists some examples of different fungal strategies for obtaining nutrients drag terms into correct categories: 1.) decomposers 2.) mutualists 3.) parasites

1.) fungi in association with a fallen log fungi in association with a dead rabbit coprophilous fungi 2.) mycorrhizal fungi on pine tree roots fungi in the family Lepiotaceae 3.)Septobasidium spp. and an individual scale insect infected by fungal hyphae Cordyceps spp. Trichophyton spp. Cryphonectria parasitica Correct Fungi have diverse ecological niches, with most fungi being decomposers. Other fungi exist in mutualistic associations. For example, it is estimated that over 85% of plants have mycorrhizal fungi living on their roots; the fungi provide the plants with inorganic nutrients, while receiving organic nutrients in return. Still other fungi are parasites, causing harm to the organisms they live with.

In some instances of reproduction in fungi, mating types function as sexes. Which of the following is a result? A.) Pollination B.) An increase in genetic diversity, which might result in an exponential number of new species C.) A decrease in genetic diversity D.) No opportunity for individuals with different alleles to mate

ANSWER B.) An increase in genetic diversity, which might result in an exponential number of new species WHAT YOU NEED TO KNOW Instead of having just two sexes, a single fungal species may have tens of thousands of sexes. The basidiomycete Schizophyllum commune, for example, is estimated to have 28,000 mating types. This could lead to an increase in genetic diversity, which might result in an exponential number of new species. The leading hypothesis to explain the existence of mating types is that they help generate genetic diversity in offspring by increasing the probability of outcrossing. Pollination does not have any bearing in this process. Hyphae of the same mating type will not combine during sexual reproduction. When zygomycete hyphae grow close to each other, for example, they will not fuse unless the individuals have different alleles of one or more genes involved in mating.

Many plants grow significantly faster when they can form mycorrhizal associations with soil fungi. Which of the following explains this finding? A.) Fungi break down lignin and cellulose. B.) When researchers added radioactive phosphorus atoms to soil, plants grown in the presence of their symbiotic fungi received more of the radioactive phosphorus than did plants grown in the absence of fungi. C.) Sugars produced by plants via photosynthesis are transferred to their fungal symbionts. D.) Many plants have endophytic fungi living in their leaves and stems.

ANSWER B.) When researchers added radioactive phosphorus atoms to soil, plants grown in the presence of their symbiotic fungi received more of the radioactive phosphorus than did plants grown in the absence of fungi. WHAT YOU NEED TO KNOW The relationship between plants and mycorrhizal fungi is mutualistic. Plants provide mycorrhizal fungi with carbohydrates. Mycorrhizal fungi supply host plants with nutrients. When researchers added radioactive phosphorus atoms to soil, plants grown in the presence of their symbiotic fungi received more of the radioactive phosphorus than did plants grown in the absence of fungi. Lignin peroxidase catalyzes the removal of a single electron from an atom in the ring structures of lignin. This oxidation step creates a free radical—an atom with an unpaired electron. This is an extremely unstable electron configuration, and it leads to a series of uncontrolled and unpredictable reactions that split the polymer into smaller units. Biologists have referred to this mechanism of lignin degradation as enzymatic combustion. Once lignin peroxidase has softened wood by stripping away its lignin matrix, the long strands of cellulose that remain can be attacked by cellulases. Like lignin peroxidase, cellulases are secreted into the extracellular environment by fungi. But unlike the uncontrolled chain reaction catalyzed by lignin peroxidase, degradation of cellulose by cellulases is extremely predictable. Experiments with isotopes used as tracers have shown that sugars and other carbon-containing compounds produced by plants via photosynthesis are transferred to their fungal symbionts. Recent research has shown that some endophytes increase the drought tolerance of their host plants. Endophytes found in some grasses also produce compounds that benefit plants. The compounds deter or even kill herbivores. In exchange for these benefits, endophytes absorb sugars from the plant. Despite these associations, the endophytes do not increase plant growth.

The fungus used to produce penicillin and other antibiotics is classified as a member of the __________. A.) Chytridiomycota B.) Basidiomycota C.) Zygomycota D.) Ascomycota

ANSWER D.) Ascomycota WHAT YOU NEED TO KNOW The fungus used to produce penicillin and other antibiotics is classified as a member of the Ascomycota. Some saprophytic ascomycetes can grow on jet fuel or paint and are used to help clean up contaminated sites. Penicillium is an important source of antibiotics, and Aspergillus produces citric acid used to flavor soft drinks and candy. The most common zygomycota are the ones that cover decaying strawberries, and many recognize the zygomycete responsible for black bread mold. EMF are enormously important in forestry. The temperate forests where these fungi are particularly abundant provide most of the hardwoods and softwoods used in building construction, furniture-making, and papermaking. Chytridiomycota are aquatic fungi responsible for the decline in amphibian populations worldwide.

Consider two hyphae that have equal dimensions: one from a septate species and the other from a coenocytic species. Compared with the septate species, the coenocytic species should have __________. A.) more chitin B.) less cytoplasm C.) more pores D.) less chitin

ANSWER D.) less chitin

Unicellular fungi, regardless of phylogenetic group, are referred to as __________. A.) molds B.) lichens C.) morels D.) yeasts

ANSWER D.) yeasts

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 of others that do not have a sexual stage? 1. They are currently classified among the ascomycetes. 2. They do not form heterokaryons. 3. Their spores are probably produced by mitosis. 4. They form dikaryotic mycelium. 5. The spores undergo crossing over during meiosis.

ANSWER 2 and 3 WHAT YOU NEED TO KNOW The correct answer is 2 and 3: They do not form heterokaryons, and their spores are probably produced by mitosis. Many species of fungi have never been observed reproducing sexually. Most species can produce haploid spores either sexually or asexually, however. During asexual reproduction, spore-forming structures are produced by a haploid mycelium, and spores are generated by mitosis. As a result, offspring are clones—meaning that they are genetically identical to their parent. In fact, large numbers of ascomycetes have never been observed to reproduce sexually. Heterokaryons contain multiple, genetically different cells.

Which of the following cells or structures are associated with asexual reproduction in fungi? A.) Conidia B.) Zygosporangia C.) Ascospores D.) Basidiospores

ANSWER A.) Conidia

What characteristic is shared by glomeromycota, basidiomycota, and ascomycota? A.) They all form spores. B.) They are all monophyletic. C.) They are all land plants. D.) They are incapable of forming mutualistic associations.

ANSWER B.) They are all monophyletic. WHAT YOU NEED TO KNOW The characteristic shared by glomeromycota, basidiomycota, and ascomycota is that they are all monophyletic. Glomeromycota is a monophyletic group of soil fungi that form arbuscular mycorrhizae with most land plants. Basidiomycota is a monophyletic group of terrestrial fungi that form four airborne spores on each club-shaped basidium within mushrooms, brackets, and puffballs. Some can degrade wood. Others form ectomycorrhizae with certain trees. Ascomycota is a monophyletic group of terrestrial fungi that form eight airborne spores in each ascus. Some form lichens in association with green algae or cyanobacteria. Each is a lineage of fungi, not land plants. Each group is capable of forming mutualistic associations with other groups. Microsporidia are parasitic, single-celled fungi with reduced genomes and an unusual polar tube used to infect host cells. Chytrids are usually aquatic with motile, flagellated spores. Some are terrestrial decomposers, and some are parasites. Zygomycetes are largely saprophytic on dead plant tissue. During sexual reproduction, they form zygosporangia after hyphae from different mating types are yoked.

During an experiment intended to determine whether an organism is a fungus, the organism is placed in a petri dish with a small piece of wood. Which of the following results would support the hypothesis that the unknown organism is indeed a fungus? The presence of __________. A.) decomposing bacteria in the dish B.) glucose in the dish C.) lignin in the dish D.) the presence of microsporidia

ANSWER B.) glucose in the dish

Penicillium is a saprophytic ascomycota that __________. A.) frequently appears on lawns as groups of fairy ring mushrooms B.) is a bluish-colored genus of mold that produces powerful antibacterial agents C.) releases thick-walled zygospores D.) is a typical club fungus

ANSWER B.) is a bluish-colored genus of mold that produces powerful antibacterial agents

Which fungal class is correctly matched with its most common habitat? A.) Ectomycorrhizal fungi (EMF); warm climate forests B.) Arbuscular mycorrhizal fungi (AMF); northern coniferous forests C.) Arbuscular mycorrhizal fungi (AMF); grasslands D.) Ectomycorrhizal fungi (EMF); tropics

ANSWER C.) Arbuscular mycorrhizal fungi (AMF); grasslands WHAT YOU NEED TO KNOW Arbuscular mycorrhizal fungi is correctly matched with grasslands, its most common habitat. AMF (arbuscular mycorrhizal fungi) are found in a whopping 80 percent of all land plant species. They are particularly common in grasslands and in tropical forests. EMF like the one shown in the figure are found on many of the tree species in the temperate regions of the world, where warm summers alternate with cold winters.

During an experiment intended to determine whether an organism is a fungus, the organism is placed in a petri dish with a small piece of wood. Which of the following results would support the hypothesis that the unknown organism is indeed a fungus? The presence of __________. A.) lignin in the dish B.) the presence of microsporidia C.) glucose in the dish D.) decomposing bacteria in the dish

ANSWER C.) glucose in the dish WHAT YOU NEED TO KNOW The presence of glucose in the dish supports the hypothesis that the organism is a fungus. Biologists have purified seven different cellulases from the fungus Trichoderma reesei. Two of these enzymes catalyze a critical early step in digestion—they cleave long strands of cellulose into the disaccharide cellobiose. The other cellulases are equally specific and also catalyze hydrolysis reactions. In combination, the suite of seven enzymes in T. reesei transforms long strands of cellulose into a simple monomer—glucose—that the fungus can absorb and use as a source of food. About half of the ascomycetes grow in mutualistic association with cyanobacteria and/or single-celled green algae, forming lichens. There are about 1,300 known species of microsporidia, and all are parasites of animal cells, especially of insects or fish. They do not degrade cellulose in wood. Fungi that absorb nutrients from dead organisms are the world's most important decomposers. Although a few types of organisms are capable of digesting the cellulose in plant cell walls, certain fungi and a handful of bacterial species are the only organisms capable of digesting both the lignin and cellulose that make up wood

Consider two hyphae that have equal dimensions: one from a septate species and the other from a coenocytic species. Compared with the septate species, the coenocytic species should have __________. A.) less cytoplasm B.) more chitin C.) more pores D.) less chitin

ANSWER D.) less chitin WHAT YOU NEED TO KNOW Compared with the septate species, the coenocytic species should have less chitin. Chitin is a prominent component of the cell walls of fungi. Because the coenocytic (aseptate) hyphae lack septate, there would be less chitin due to the cell containing multiple nuclei being divided into separate cells. Septate species have hyphae with distinct divisions where separate cells are observed. Some fungal lineages have hyphae that are coenocytic ("common-celled"; pronounced see-no-SIT-ick)—meaning that they are not divided into separate cells and thus lack septa. Coenocytic fungi have hundreds or thousands of nuclei scattered throughout the mycelium. In effect, they are a single, gigantic, multinucleate cell. The coenocytic cell would exhibit more cytoplasm and fewer pores.

Which feature seen in chytrids supports the hypothesis that they diverged earliest in fungal evolution? Flagellated spores Parasitic lifestyle Coenocytic hyphae Formation of resistant zygosporangia

ANSWER Flagellated spores WHAT YOU NEED TO KNOW Flagellated spores seen in chytrids supports the hypothesis that they diverged earliest in fungal evolution. Fossils of fungi are very rare, so biologists rely on morphological and molecular data to explore their past. Because most fungi form mycelia, and because this body type is so fundamental to the absorptive mode of life, most studies of fungal morphology have focused on them. Chytrids are usually aquatic with motile, flagellated spores. Some are terrestrial decomposers, and some are parasites. Some fungal lineages have hyphae that are coenocytic ("common-celled"; pronounced see-no-SIT-ick)—meaning that they are not divided into separate cells and thus lack septa. Coenocytic fungi have hundreds or thousands of nuclei scattered throughout the mycelium. In effect, they are a single, gigantic, multinucleate cell.

The Greek root ecto refers to "outer." Why does this term accurately describe EMF? It has a mutualistic relationship to cyanobacteria. It is found in the majority of land plant species. In this type of association, hyphae form a dense network that covers the outer sheath of a plant's root tips. Hyphae grow into the cells of root tissue.

ANSWER In this type of association, hyphae form a dense network that covers the outer sheath of a plant's root tips.

Most fungal species that undergo sexual reproduction produce one of four types of distinctive reproductive structures. Which of these responses is not one of these four types? Swimming gametes and spores Basidia Asci Pores Zygosporangia

ANSWER Pores WHAT YOU NEED TO KNOW Pores are not one of the four distinctive reproductive structures found among fungal species. Image depicting the four types of sexual reproductive structures that are observed in fungi: (A) swimming gametes and spores, (B) zygosporangia, spore-producing structures formed when hyphae are yoked, (C) basidia, club-shaped cells that undergo meiosis, and (D) asci, saclike cells in which meiosis and one round of mitosis occur. The other four responses are correct: Swimming gametes and spores: In certain species that live primarily in water or wet soils, the gametes produced during sexual reproduction have flagella, as do the spores produced during asexual reproduction. These are the only motile cells known in fungi. Species with swimming gametes are traditionally known as chytrids (pronounced KYE-trids). Zygosporangia: In some species, haploid hyphae from two individuals meet and become joined, like oxen with a yoke. Cells from yoked hyphae fuse to form a distinctive spore-producing zygosporangium (plural: zygosporangia). Species with a zygosporangium are traditionally known as zygomycetes. Basidia: Mushrooms, brackets, and puffballs form specialized clublike cells called basidia (singular: basidium; "little-club") at the ends of hyphae, each producing four spores. Species with basidia are traditionally called basidiomycetes or "club fungi." Asci: Cups, morels, and some other types of fungi form specialized saclike cells called asci (singular: ascus) at the ends of hyphae, on the surfaces of the fungi, each producing eight spores. Species with asci are traditionally known as ascomycetes or "sac fungi."

Fungi have an extremely high surface-area-to-volume ratio. What is the advantage of this ratio to an organism that gets most of its nutrition through absorption? The lower volume prevents the cells from drying out too quickly, which can interfere with absorption. The larger surface area allows more material to be transported through the cell membrane. The high ratio creates more room inside the cells for additional organelles involved in absorption. The high ratio means that fungi have a thick, fleshy structure that allows them to store more of the food they absorb.

ANSWER The larger surface area allows more material to be transported through the cell membrane.

The photosynthetic symbiont of lichens is often __________. a green algae a moss a brown algae an ascomycete

ANSWER a green algae

The multicellular condition of animals and fungi seems to have arisen __________. by convergent evolution by natural means, and is a homology by inheritance of acquired traits due to common ancestry

ANSWER by convergent evolution WHAT YOU NEED TO KNOW The multicellular condition of animals and fungi seems to have arisen by convergent evolution. The close evolutionary relationship between fungi and animals explains why fungal infections in humans are much more difficult to treat than bacterial infections. Fungi and humans shared a common ancestor relatively recently.

Symbiotic partnerships in which one partner benefits and the other is unaffected are called __________. mutualistic parasitic endophytic commensal

ANSWER commensal

Which of the following is required to make bread dough rise? a.) Mycorrhizal fungus b.) Mutualistic fungus c.) Saprophytic fungus d.) Saccharomyces cerevisiae

ANSWER d.) Saccharomyces cerevisiae

Which of the following statements is true of parasitic fungi? A.) The major destructive impact of fungi on humans is through illness. b.) American elm and chestnut trees quickly developed genetic resistance to an introduced fungal pathogen. c.) The majority of fungal species are not important in promoting human health. d.) The incidence of fungal infections in human populations is low when compared to the frequency of diseases caused by bacteria, viruses, and protists.

ANSWER d.) The incidence of fungal infections in human populations is low when compared to the frequency of diseases caused by bacteria, viruses, and protists. WHAT YOU NEED TO KNOW It is true that the incidence of fungal infections in human populations is low when compared to the frequency of diseases caused by bacteria, viruses, and protists. The major destructive impact that fungi have on people is through the food supply. In nature, epidemics caused by fungi have killed 4 billion chestnut trees and tens of millions of American elm trees in North America. The fungal species responsible for these epidemics were accidentally imported on species of chestnut and elm native to other regions of the world. When the fungi arrived in North America and began growing in chestnuts and elms native to North America, the results were catastrophic. Local chestnut and elm populations had virtually no genetic resistance to the pathogens and quickly succumbed. But even though these maladies can be serious, in reality, no more than approximately 200 species of fungi—out of the hundreds of thousands of existing species—regularly cause illness in humans. Fungi are very important in promoting human health. The first antibiotic that was widely used, penicillin, was isolated from a fungus, and soil-dwelling fungi continue to be the source of many of the most important antibiotics prescribed against bacterial infections.

Mycorrhizae are to the roots of vascular plants as endophytes are to vascular plants' __________. leaf mesophyll waxy cuticle xylem shoot apical meristems

ANSWER leaf mesophyll

Saprophytic fungi __________. get their name from their habit of feeding upon the sap leaking from injured trees absorb small molecules from the cells of living hosts are not common enough to be worth studying release enzymes that partially digest dead tissues

ANSWER release enzymes that partially digest dead tissues WHAT YOU NEED TO KNOW Saprophytic fungi release enzymes that partially digest dead tissues. Saprophytic fungi are master recyclers. Although bacteria and archaea are also important decomposers in terrestrial environments, some fungi and a few bacterial species are the only organisms that can digest wood completely. Given enough time, fungi can turn even the hardest, most massive trees into soft soils. Saprophytic fungi can grow toward the dead tissues that supply their food. Saprophytic fungi are like miners. But instead of seeking out rare, gemlike nitrogen or phosphorus atoms, as do EMF and AMF, saprophytes use lignin peroxidase to blast away enormous lignin molecules, exposing rich veins of cellulose that can fuel growth and reproduction.

What do fungi and arthropods have in common? A.) The haploid state is dominant in both groups. B.) Both groups are predominantly autotrophs that produce their own food. C.) Both groups are commonly coenocytic. D.) Chitin is the main component of cell walls in fungi and the exoskeleton of arthropods.

ANSWER D.) Chitin is the main component of cell walls in fungi and the exoskeleton of arthropods. WHAT YOU NEED TO KNOW Chitin is a prominent component of the cell walls of fungi and the exoskeleton of arthropods. Some fungal lineages have hyphae that are coenocytic ("common-celled"; pronounced see-no-SIT-ick)—meaning that they are not divided into separate cells and thus lack septa. Coenocytic fungi have hundreds or thousands of nuclei scattered throughout the mycelium. In effect, they are a single, gigantic, multinucleate cell. Fungi are both haploid and diploid. Arthropods are primarily diploid. Fungi and arthropods are heterotrophs. They get energy and nutrients from the food they consume.

Which hyphal feature is key to the way a fungal mycelium obtains food? a. Mushrooms b. Thin filamentous shape c. Septa d. Septal pores

ANSWER B.) Thin filamentous shape WHAT YOU NEED TO KNOW: A thin filamentous shape is key to the way a fungal mycelium obtains food. -Hyphae (singular: hypha) are the filaments within a mycelium. As the figure shows, hyphae are long, narrow filaments that branch frequently. Because mycelia are composed of complex, branching networks of extremely thin hyphae, fungi have the highest surface-area-to-volume ratios observed in multicellular organisms and are therefore the best at absorption. -In most terrestrial fungi, each filament is divided into cells by cross-walls called septa (singular: septum). Septa do not close off the cells along hyphae completely. Instead, gaps called pores enable a wide variety of materials, even nuclei and other organelles, to flow from one compartment to the next. -While not as "helpful" as the thin, branching hyphae in obtaining food, the fact that cells are divided by septae and not full cell walls can also allow the mycelium to grow and obtain food due to cytoplasmic streaming. -One advantage of most fungi having pores in septa is that nutrients can move rapidly from regions of uptake to regions of mycelial growth.

Which conclusion drawn from the phylogeny shown above best explains these morphological traits in living fungal lineages: chitin in fungal cell walls, flagella in chytrid spores and gametes, and the storage of food through synthesis of glycogen? A.)Fungi are more closely related to animals than they are to land plants. B.) The early ancestor of the fungi was a green plant. C.) The early ancestor of the fungi was a green alga. D.) Fungi share a common ancestor with choanoflagellates.

ANSWER= A.)Fungi are more closely related to animals than they are to land plants. WHAT YOU NEED TO KNOW The figure shows that fungi are more closely related to animals than they are to land plants. Fungi and humans shared a common ancestor relatively recently. The sister group to animals, choanoflagellates, comprises animals as well as protists, and are solitary or colonial protists found in freshwater.

If all of their nuclei are equally active transcriptionally, the cells of dikaryotic fungi, in terms of the gene products they can make, are essentially __________. A.)haploid B.)diploid C.)alloploid D.)completely homozygous

ANSWER= B.)diploid WHAT YOU NEED TO KNOW If all of their nuclei are equally active transcriptionally, the cells of dikaryotic fungi, in terms of the gene products they can make, are essentially diploid. Most hyphae in heterokaryotic mycelia are dikaryotic ("two kernel")—they are divided by septa, and each cell contains two nuclei, one from each mating type. The distinct nuclei in dikaryotic and heterokaryotic mycelia function independently, even though gene expression must be coordinated for growth and development to occur. For example, in septate fungi, the two types of nuclei divide as the hyphae expand, so each compartment that is divided by a septum contains one of each of the two types of nuclei.

Which description does not apply equally well to both sexual and asexual spores? A.) Upon germination, they will subsequently undergo S phase and mitosis. B.)They represent the dispersal stage. C.)They have haploid nuclei. D.)They are produced by meiosis

ANSWER= D.)They are produced by meiosis. WHAT YOU NEED TO KNOW "They are produced by meiosis" does not apply equally well to both sexual and asexual spores. During asexual reproduction, spore-forming structures are produced by a haploid mycelium, and spores are generated by mitosis. Spores are a dispersal stage for fungi. Among the sexually reproducing species of fungi, the presence of a heterokaryotic stage and the morphology of the spore-producing structure vary.

Which of the following fungi are parasitic? a.) Athlete's foot fungus b.) Arbuscular mycorrhizal fungi (AMF) c.) Saprophytes d.) Lichens

ANSWER= a.) Athlete's foot fungus WHAT YOU NEED TO KNOW Athlete's foot fungus is parasitic. When fungi absorb nutrients without providing any benefit in return, they lower the fitness of their host organism and act as parasites. Athlete's foot fungus and vaginal yeast infections are parasitic fungi. The name arbuscular ("little-tree") was inspired by the bushy, highly branched hyphae, shown in the figure, that form between the cell walls and the plasma membrane of root cells. AMF are also called endomycorrhizal fungi because they penetrate the interior of root cell walls. Saprophytic fungi are like miners. But instead of seeking out rare, gemlike nitrogen or phosphorus atoms, as do EMF and AMF, saprophytes use lignin peroxidase to blast away enormous lignin molecules, exposing rich veins of cellulose that can fuel growth and reproduction. About half of the ascomycetes grow in mutualistic association with cyanobacteria and/or single-celled green algae, forming lichens.

Which of the following statements correctly describes the evolution of fungi, according to current hypotheses? A.) Basidiomycetes and ascomycetes arose first, followed by chytrids. b.) Basidiomycota and Ascomycota are distantly related sister groups to fungi. c.) The earliest fungi were aquatic. D.) Zygomycetes emerged first, then chytrids, and later Basidiomycota and Ascomycota.

ANSWER= c.) The earliest fungi were aquatic. WHAT YOU NEED TO KNOW Because choanoflagellates and the most ancient groups of animals are aquatic, and because chytrids are aquatic, it is reasonable to hypothesize that the earliest fungi were aquatic and that the switch to terrestrial life occurred early in the evolution of the fungi. Together, the Basidiomycota and Ascomycota form a monophyletic group. Because basidiomycetes and ascomycetes both form septate hyphae and large "fruiting" structures, this growth habit evolved once. The chytrids and zygomycetes are poorly resolved. The actual order of branching events among lineages with these reproductive structures is still not known (in the figure below, they are collapsed into a polytomy).

Which group of fungi is largely aquatic? a.)Chytrids b.)Zygomycetes c.)Basidiomycetes d.)Glomeromycetes

ANSWER= A.) Chytrids WHAT YOU NEED TO KNOW: *Chytrids are largely aquatic and are common in freshwater environments.* The zygomycetes ("yoked fungi") are primarily soil dwellers. Along with a few soil-dwelling bacteria, some members of this lineage are the only organisms capable of synthesizing lignin peroxidase and are therefore important in wood decomposition. Glomeromycetes are often found in association with terrestrial plant roots. All members of this group (except for a single species) comprise the arbuscular mycorrhizal fungi (AMF).

Biologists concluded that the phylogeny in the figure above represents the best estimate currently available for the history of fungi. Which of the following represents one of the conclusions supported by this research? A.) Microsporidians are close relatives of fungi but are not included in fungal lineages. B.)The relationships between and among chytrids and zygomycetes are poorly resolved. C.) Ascomycota are paraphyletic. D.)Basidiomycota and Ascomycota form a polytomy.

ANSWER= B.)The relationships between and among chytrids and zygomycetes are poorly resolved. WHAT YOU NEED TO KNOW The relationships between and among chytrids and zygomycetes are poorly resolved. The actual order of branching events among lineages with these reproductive structures is still not known (in the figure below, they are collapsed into a polytomy). The single-celled, parasitic eukaryotes called microsporidians are actually fungi. Interpretation: They are not a distantly related sister group to fungi, as initially thought. This point is important. Researchers are now testing the hypothesis that fungicides—molecules that are lethal to fungi—can cure microsporidian infections in bee colonies, silkworm colonies, and AIDS patients. Ascomycetes are monophyletic—they form a lineage called Ascomycota, or sac fungi. This means that the ascus evolved once. Together, Basidiomycota and Ascomycota form a monophyletic group.

Identify the two growth forms of fungi. A.)Hyphae and mycelia B.)Mycelia and chytrids C.)Yeasts and mycelia D.)Chytrids and zygomycetes

ANSWER= C.)Yeasts and mycelia WHAT YOU NEED TO KNOW Yeasts and mycelia are the two growth forms of fungi. Compared with animals and land plants, fungi have simple bodies. Only two growth forms occur among them: (1) single-celled forms called yeasts, and (2) multicellular, filamentous structures called mycelia (singular: mycelium). Many species of fungus grow either as yeasts or as mycelia, but some regularly adopt both growth forms. The filaments within a mycelium are called hyphae (singular: hypha). As the figure shows, hyphae are long, narrow filaments that branch frequently. In certain species that live primarily in water or wet soils, the gametes produced during sexual reproduction have flagella, as do the spores produced during asexual reproduction. These are the only motile cells known to exist in fungi. Species with swimming gametes are traditionally known as chytrids (pronounced KYE-trids). Species with a zygosporangium are traditionally known as zygomycetes.

Using the known traits and lifestyle patterns of arbuscular mycorrhizal fungi (AMF), select the most likely AMF association from the choices below. a.)A glomeromycete species whose hyphae grow into the root cells of grassland plants in warm, low-phosphorus soils b.)A zygomycete species whose hyphae grow into the root cells of northern birch trees c.)A glomeromycete species whose hyphae network extends between, and not into, root cells of plants in cool soils high in phosphorus d.)A zygomycete species whose hyphae extend between, and not into, root cells of trees in warm, low-phosphorus soils

ANSWER=A.) A Glomeromycete species whose hyphae grow into the root cells of grassland plants in warm, low-phosphorous soils. WHAT YOU NEED TO KNOW: *Using the known traits and lifestyle patterns of arbuscular mycorrhizal fungi (AMF), the most likely AMF association would be a glomeromycete species whose hyphae grow into the root cells of grassland plants in warm, low-phosphorus soils.* -AMF absorb phosphorus-containing ions or molecules in the soil and transfer them, along with other nutrients and water, into the roots of most of the plants living in grasslands and tropical forests. In exchange, the host plant provides the symbiotic fungi with sugars and other organic compounds. -EMF are more often associated with birch trees, which are more common in temperate climates. Researchers have found that when birch tree seedlings are grown with and without their normal EMF in pots filled with forest soil, only the seedlings with EMF are able to acquire significant quantities of nitrogen and phosphorus. Inspired by such data, one biologist has referred to ectomycorrhiza as the "dominant nutrient-gathering organs in most temperate forest ecosystems."

Which of the following statements is true of lichens? a.)Lichens are the most prevalent colonizers of bare rock surfaces throughout the world. b.)In most lichens, the fungus involved is a basidiomycete, although a few are ascomycetes. c.)Only several hundred lichens have been described to date, but many more are thought to exist. d.)Fungi in lichens provide carbohydrates and phosphorus to the cyanobacterium or alga.

ANSWER=A.)Lichens are the most prevalent colonizers of bare rock surfaces throughout the world. WHAT YOU NEED TO KNOW: *Lichens are the most prevalent colonizers of bare rock surfaces throughout the world.* -About half of the ascomycetes grow in mutualistic association with cyanobacteria and/or single-celled green algae, forming lichens. Over 17,500 different lichens have been described to date; in most, the fungus involved is an ascomycete (although a few basidiomycetes participate as well). -In abundance and diversity, lichens dominate the Arctic and Antarctic tundras and are extremely common in boreal forests. They are the major food of caribou in the winter as well. -The fungus in lichens appears to protect the photosynthetic bacterial or algal cells. The fungal hyphae form a dense protective layer that shields the photosynthetic species and reduces water loss. In return, the cyanobacterium or alga provides carbohydrates that the fungus uses as a source of carbon and energy.

How are cellulase enzymes similar to lignin peroxidase? A.) Cellulases and lignin peroxidase are extremely specific in their action. B.)Cellulases and lignin peroxidase are extracellular digestive enzymes. C.) Cellulases and lignin peroxidase cleave long strands of cellulose into cellobiose. C.)Cellulases and lignin peroxidase catalyze hydrolysis reactions.

ANSWER=B.) Cellulases and lignin peroxidase are extracellular digestive enzymes. WHAT YOU NEED TO KNOW: Cellulases and lignin peroxidase are extracellular digestive enzymes. Unlike the uncontrolled chain reaction catalyzed by lignin peroxidase, degradation of cellulose by cellulases is extremely predictable. Biologists have purified seven different cellulases from the fungus Trichoderma reesei. Two of these enzymes catalyze a critical early step in digestion—they cleave long strands of cellulose into the disaccharide cellobiose. The other cellulases are equally specific and also catalyze hydrolysis reactions. By contrast, lignin peroxidase catalyzes the removal of a single electron from an atom in the ring structures of lignin. This oxidation step creates a free radical—an atom with an unpaired electron. This is an extremely unstable electron configuration, and it leads to a series of uncontrolled and unpredictable reactions that split the polymer into smaller units. Biologists have referred to this mechanism of lignin degradation as enzymatic combustion.

Endophytes are fungi that live in and on the leaves and stems of vascular plants. Which of the following statements about endophytes is correct? A.) Endophytes have been studied for many years and are well understood. B.) Some species of endophytes are commensals, meaning that the two species, endophyte and plant, coexist without substantial deleterious or beneficial effects. c.) Endophytes are rarely found in nature. D.) Endophytes include the two groups of mycorrhizal fungi.

ANSWER=B.) Some species of endophytes are commensals, meaning that the two species, endophyte and plant, coexist without substantial deleterious or beneficial effects. WHAT YOU NEED TO KNOW Biologists have concluded that the relationship between endophytes and some plants is mutualistic. In other types of plants, however, researchers have not been able to document benefits for the plant host. These species of endophytes are commensals, meaning that the two species, endophyte and plant, coexist without substantial deleterious or beneficial effects. Commensal means simply to live together. This is different than a commensalism where one species benefits and the other is not affected. Not long after associations between fungi and the roots of land plants were discovered, researchers found that two types of plant-mycorrhizal interactions are particularly common, involving ectomycorrhizal fungi (EMF) and arbuscular mycorrhizal fungi (AMF). Endophytic fungi were unknown before the 1940s; they are turning out to be both extremely common and highly diverse. When plants are alive, mycorrhizal fungi are often found associated with their roots, and many fungal species grow as endophytes.

Biologists divide fungi into four different groups based on __________. A.)the different environments where groups of fungi live B.) whether fungi reproduce sexually or asexually C.) the amount of surface area offered by the mycelia D.) their distinctive reproductive structures

ANSWER=D.) their distinctive reproductive structures WHAT YOU NEED TO KNOW Biologists divide fungi into four different groups based on their distinctive reproductive structures. Most fungal species that undergo sexual reproduction produce one of four types of distinctive reproductive structures: swimming gametes and spores, zygosporangia, basidia, and asci. The extraordinarily high surface area in a mycelium has a downside, however. The amount of water that evaporates from an organism is a function of its surface area—meaning that these organisms are prone to drying out. As a result, fungi are most abundant in moist habitats. All fungi have mycelia adapted to maximize their surface-area-to-volume ratio, thus enhancing their absorptive ability.

Why are associations between ectomycorrhizal fungi (EMF) and plant roots more common in a Canadian forest than in a Mexican swamp? a.)EMF are most commonly found in temperate climates. b.)EMF are found only on a very few coniferous species in the far north. c.)In colder areas, EMF metabolism raises the soil temperature, increasing productivity. D.)Mycorrhizal associations are uncommon in warm climates.

ANSWER=a.)EMF are most commonly found in temperate climates. WHAT YOU NEED TO KNOW: *Associations between ectomycorrhizal fungi (EMF) and plant roots more common in a Canadian forest than in a Mexican swamp because EMF are most commonly found in temperate climates.* -EMF are found on many of the tree species in the temperate regions of the world, where warm summers alternate with cold winters.

What enzyme do fungi use to digest lignin? a.)Lignin peroxidase b.)Lignin digesterase c.)Lignin cellulase d.)Lignin oxidase

ANSWER=a.)Lignin peroxidase WHAT YOU NEED TO KNOW: *Lignin peroxidase catalyzes the removal of a single electron from an atom in the ring structures of lignin.* Like lignin peroxidase, cellulases are secreted into the extracellular environment by fungi. But unlike the uncontrolled chain reaction catalyzed by lignin peroxidase, degradation of cellulose by cellulases is extremely predictable.

When food sources are depleted, hyphae respond by making spores. Why? a. The leading hypothesis is that spore production is favored by natural selection when hyphae are under nutritional stress. b. The leading hypothesis is that fungi change feeding mechanisms once food can no longer be absorbed, and spore production is a by-product of this change. c. The leading hypothesis is that spore production attracts animals, which can be used to transport the fungi to an area where more food is available. d. The leading hypothesis is that spore production allows fungi to harvest food particles that are floating in the air.

ANSWER=a.)The leading hypothesis is that spore production is favored by natural selection when hyphae are under nutritional stress. WHAT YOU NEED TO KNOW: *When food sources are depleted, hyphae respond by making spores. The leading hypothesis is that spore production is favored by natural selection when hyphae are under nutritional stress.* Spore production allows starving mycelia to disperse offspring to new habitats where more food might be available. Thus, spore production is favored by natural selection when individuals are under nutritional stress. As the fungus expands, hyphae grow in the direction in which food is most abundant. But if food begins to run out, mycelia respond by making spores, which are dispersed by wind or animals

Which process occurs in fungi and has the opposite effect on a cell's chromosome number than does meiosis I? A.)Karyogamy B.)Plasmogamy C.)Crossing over D.)Mitosis

Answer= A.)Karyogamy WHAT YOU NEED TO KNOW: *In a dikaryotic or heterokaryotic mycelium, one or more pairs of unlike nuclei may eventually fuse to form a diploid zygote. The fusion of nuclei is karyogamy (pronounced ka-ree-AH-gamee). The nuclei that are produced by karyogamy then divide by meiosis to form haploid spores.* -The spore is the most fundamental reproductive cell in fungi. Spores are the dispersal stage in the fungal life cycle and are produced during both asexual and sexual reproduction. (Asexual reproduction is based on mitosis, whereas sexual reproduction is based on meiosis.) Fungi produce spores in such prodigious quantities that it is not unusual for them to outnumber pollen grains in air samples. -In many fungi, the process of sexual reproduction begins when hyphae from two different mating types fuse to form a hybrid cell. When the cytoplasm of two individuals fuses in this way, plasmogamy (pronounced plaz-MAH-ga-mee) is said to occur.

Immediately after karyogamy occurs, which term applies? a.)Diploid b.)Plasmogamy c.)Heterokaryotic d.)Dikaryotic

Answer= a.) Diploid In a dikaryotic or heterokaryotic mycelium, one or more pairs of unlike nuclei may eventually fuse to form a diploid zygote. -The fusion of nuclei is karyogamy (pronounced ka-ree-AH-gamee). The nuclei that are produced by karyogamy then divide by meiosis to form haploid spores. -In many fungi, the process of sexual reproduction begins when hyphae from two different mating types fuse to form a hybrid cell. When the cytoplasm of two individuals fuses in this way, plasmogamy (pronounced plaz-MAH-ga-mee) is said to occur. -When two or more genetically distinct nuclei exist within a single mycelium, it is heterokaryotic ("different kernel"). -Most hyphae in heterokaryotic mycelia are dikaryotic ("two kernel")—they are divided by septa, and each cell contains two nuclei, one from each mating type.

Select the correct statement about the process of karyogamy. a.) Karyogamy produces a diploid reproductive stage. b.) Karyogamy forms yoked hyphae. c.) Karyogamy produces gametes. D.) Plasmogamy immediately precedes karyogamy.

Answer= a.) Karyogamy produces a diploid reproductive stage. Only the zygomycetes form yoked hyphae. Only chytrids produce gametes. Plasmogamy does occur before karyogamy, but, often, plasmogamy does not immediately lead to nuclear fusion. Rather, the genetically distinct haploid nuclei persist in the same cell or mycelium.

The following statements describe something about the body structures or functions of fungi. Identify those statements that are correct. a.) Nutrients can flow through the entire mycelium in fungi with coenocytic hyphae, but not in fungi with septate hyphae. b.) Some fungi secrete digestive enzymes into the environment and then absorb the digested nutrients. c.) All fungi are heterotrophs; some species live as decomposers and others as symbionts. d.) Cellulose gives rigidity and strength to the cell walls of fungi. e.) Some fungi can grow as either filamentous or single-celled forms. f.) Mycelia are made up of small-diameter hyphae that form an interwoven mass, providing more surface area for nutrient absorption

Answers b.) Some fungi secrete digestive enzymes into the environment and then absorb the digested nutrients. c.) All fungi are heterotrophs; some species live as decomposers and others as symbionts. e.) Some fungi can grow as either filamentous or single-celled forms. f.) Mycelia are made up of small-diameter hyphae that form an interwoven mass, providing more surface area for nutrient absorption Correct All fungi are heterotrophs. Most obtain carbon compounds by decomposing organic matter, while others live in a symbiotic association with other organisms. The feeding structure of a multicellular fungus is the mycelium, which consists of numerous small-diameter filaments, or hyphae. Nutrients absorbed by the hyphae can flow throughout the mycelium in both coenocytic hyphae and septate hyphae.

Multicellular fungi share some key traits, including their body structures, growth patterns, and methods for absorbing nutrients. However, although their feeding methods may be similar, fungal species differ markedly in their sources of nutrients, which include both living and dead organisms. As a result, fungi play a variety of roles in ecological communities. label the diagram: Structure of multicellular fungi

The body of a multicellular fungus consists of a network of hyphae, which form an interwoven mass called a mycelium. Some hyphae, called septate hyphae, are divided into cells by crosswalls, or septa. Coenocytic hyphae do not have septa; these hyphae consist of a continuous cytoplasmic mass that contains many nuclei and organelles.

karyogamy & spore stages:

The fusion of nuclei is karyogamy (pronounced ka-ree-AH-gamee). The nuclei that are produced by karyogamy then divide by meiosis to form haploid spores. The spore is the most fundamental reproductive cell in fungi. Spores are the dispersal stage in the fungal life cycle and are produced during both asexual and sexual reproduction.

Fungi

a lineage of eukaryotes that typically have a filamentous body (mycelium) and obtain nutrients by absorption.

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 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 ___________. A.) nuclei B.) centrosomes C.) the "9 + 2 pattern" of microtubules D.) lysosomes

answer C.) the "9 + 2 pattern" of microtubules WHAT YOU NEED TO KNOW Given the eukaryotic structures they lack, it should be expected that microsporidians also lack the "9 + 2 pattern" of microtubules. All flagella and cilia of eukaryotes are characterized by the so-called "9 + 2" structure.

What is the major distinguishing characteristic of fungi? A) acquiring nutrition through ingestion B) sedentary lifestyle C) prokaryotic cells D) absorbing nutrients E) decomposing dead organisms

answer= A) acquiring nutrition through ingestion

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

answer= A) animals

Why is it more difficult to treat fungal infections than bacterial infections in humans? A) Fungi are larger organisms than bacteria and thus require stronger drugs to stop an infection. B) Most fungi are multicellular and thus the drugs required to treat a fungal infection must be able to kill several types of cells; bacteria, on the other hand, are unicellular and thus simpler to kill. C) Fungal and animal cells and proteins are similar. Thus, drugs that disrupt fungal cell or protein function may also disrupt human cell or protein function. D) Fungi are able to mutate more quickly than bacteria, so they quickly develop resistance to antifungal drugs.

answer= C) Fungal and animal cells and proteins are similar. Thus, drugs that disrupt fungal cell or protein function may also disrupt human cell or protein function.

Which of these fungal features supports the phylogenetic conclusion that fungi are more closely related to animals than plants? A) Fungi are able to change their body shape continuously throughout their life. B) Zygomycetes have flagellated gametes. C) Fungi store polysaccharides as starch. D) The cell walls of fungi are made of chitin.

answer= D) The cell walls of fungi are made of chitin.

Long, branching fungal filaments are called _____. A) roots B) ascus C) septa D) mycelia E) hyphae

answer= E) hyphae

Which of the following is an important role for fungi in the carbon cycle? a.) Fungi provide fixed carbon to plants for the production of plant cellular tissues. b.) Fungi fix carbon by undergoing photosynthesis. c.) Fungi reduce atmospheric carbon dioxide. d.) Fungi release fixed carbon back to the environment for plants and photosynthetic organisms to utilize.

answer= d.) Fungi release fixed carbon back to the environment for plants and photosynthetic organisms to utilize.

Chemicals, secreted by soil fungi, which inhibit the growth of bacteria, are known as _____. a.) antibodies b.) antigens c.) hallucinogens d.) aflatoxins e.) antibiotics

answer= e.) antibiotics Explanation: Antibiotics create a zone of inhibition that inhibits bacterial growth. Depending on how effective the antibiotic is the size of the zone of inhibition increases or decreases.

Fungi that absorb nutrients from decaying plant matter are called _____. A) saprobes B) mycorrhizae C) mushrooms D) yeasts E) molds

answer= A) saprobes

Which of the following processes occurs first in sexual reproduction in many fungi? a.)Plasmogamy b.)Fusion of sperm and egg c.)Karyogamy d.)Release of spores

answer= a.)Plasmogamy occurs first in sexual reproduction in many fungi. In many fungi, the process of sexual reproduction begins when hyphae from two different mating types fuse to form a hybrid cell. When the cytoplasm of two individuals fuses in this way, plasmogamy (pronounced plaz-MAH-ga-mee) is said to occur.