Botany: An introduction to plant biology, 5 ed. Mauseth. Chapter24

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1 1 UNIT 1: FUNGI th Botany: An introduction to plant biology, 5 ed. Mauseth. Chapter24 OBJECTIVES In doing this unit you will look at representatives from several groups of the fungi and learn about the characteristics and life cycles of these phyla. By the end of the lab, you should be able to name the different phyla, identify their defining characters and understand their life cycles. In addition, we will also look at slime molds (which, while not members of Kingdom Fungi, are more closely related to Fungi than they are to other groups of protists) and at lichens. Lichens are symbiotic associations between two organisms, the photosynthetic partner a green alga and/or cyanobacteria (the phycobiont) and the fungal partner 98% of which are ascomycete and the remaining 2% basidiomycete (the mycobiont). By the end of lab, you should understand the relationship between the two organisms, be able to discuss the ecological role of lichens, and identify the different growth forms of lichens. BACKGROUND The fungi are a heterogeneous group of organisms which most people know as molds, mushrooms and toadstools seen in the woods. Traditionally fungi have been associated with botany because they are more plant-like rather than animal-like. More plant-like because they grow out of the ground, are non-motile and produce numerous spores. However, recent molecular phylogenies indicate fungi are more closely related to the ancestors of the animals than they are to plants. One trait in particular is the composition of the cell wall; while animals don t have cells walls, the cell walls of fungi are composed of chitin but the cell walls of plants are composed of cellulose. Fungal phylogeny and, by extension, classification are in a state of flux. As seen by Figure 1, there are several polyphyletic groups (notably the Chytrids and Zygomycetes). Since the Figure 1-1. A current fungal phylogeny (from Raven 2103).

2 2 taxonomy is in such a state of flux, the endings will change depending on which reference source you are currently using. Your text identifies these major groups as Classes (-mycetes) while other references have the rank as Phyla ( mycota). The Kingdom Fungi contains those organisms that are non-photosynthetic heterotrophic eukaryotes with cell walls primarily composed of chitin. Fungi obtain their food by extracellular digestion of dead or living organic material. Most are multicellular with the body of the organism comprised of filaments of cells called hyphae (hypha, singular). Even though most all Fungi reproduce both sexually as well as asexually, the different groups of fungi are classified as to how they produce sexual spores. Microsporedia (which we will not examine in lab) produce non-motile spores, but little is known about the group. Chytrids are the only group of fungi which produce flagellated gametes. Zygomycetes produce zygospores inside a zygosporangium. Ascomycetes produce eight ascospores within an ascus, while four basidiospores are formed on the outside of a basidium in Basidiomycetes. Glomeromycetes are not known to reproduce sexually. Fungi other than Chytrids and Glomeromycetes have a zygotic meiosis life cycle pattern. The general format is as follows: compatible strains of hyphae grow close together; through various methods these compatible hyphae form a specialized cell in which a haploid nucleus from each strain fuse together producing a diploid zygote; the zygote is retained in a specialized cell, a sporangium; inside the sporangium the zygote undergoes meiosis producing four haploid spores (half being "+" and half being "-" strains); and the spores are released from the sporangium into the environment. Under favorable conditions the spores germinate forming a new generation of hyphae digesting their way through the host substrate as they grow in size. (In Zygomycetes the spores sometimes germinate within the sporangium and emerge into the environment as hyphae). Under appropriate environmental conditions the new generation of hyphae mate with another compatible mating type continuing the cycle. The classes of the fungi can also be segregated by morphological differences of certain structure of the life cycle. The structures most often used in classification are hyphal anatomy and the development and morphology of the sexual sporangia. Asexual reproduction occurs in all phyla of the fungi. The method of asexual reproduction; fragmentation, asexual spores, conidia formation, or budding, are also used in classification. The hypha can be coenocytic (nuclei of different cells not separated by end walls) or can be septate (end walls separate single or pairs of nuclei). All fungi with septa have some form of perforation in the cell wall allowing cytoplasmic connections between adjoining cells. Sporangia of Zygomycetes are small simple structures formed immediately after fertilization produces the zygote. The sporangia in Ascomycetes and Basidiomycetes develop within conspicuous "fruiting bodies." These latter two groups are also unique in that when the cells of the mating hyphae fuse, the nuclei do not immediately fuse but rather form a new hypha with two nuclei in each cell (dikaryotic, n+n). The dikaryotic hypha together with other uninucleate hyphae will form the fruiting body. On specific surfaces of the fruiting body specialized cells form on the tips of the dikaryotic hyphae. The two nuclei within these terminal cells fuse in the process of karyogamy, forming the zygote. The dikaryotic hyphae of Ascomycetes and Basidiomycetes differ in the method of mitotic and meiotic division and the appearance of the sporangia and fruiting bodies. In this lab, we will look at representatives of the Chytrids, Zygomycetes, Glomeromycetes, Ascomycetes, Basidiomycetes, slime molds, and lichens. Water molds, the Oomycota, which are not related to the Fungi at all, will be covered with the Algae.

3 3 As you look at the microscope slides in this lab, look at them first with the dissecting microscope in order to determine if there is a specific part of the image that you need to focus on! EXERCISE 1: CHYTRIDS/ CHYTRIDOMYCOTA: Allmyces arbusculus 1. You have two Allomyces slides (#1-2) the sporophyte and the gametophyte. What differences do you see between them? Can you see any gametes? What do they look like? 2. Do you see anything that would make you think that this is a member of Kingdom Fungi? If so, what? EXERCISE 2: ZYGOMYCETES/ ZYGOMYCOTA: Rhizopus stolonifer The Class Zygomycetes derives its name from the thick-walled zygosporangium that forms around the zygote. Following meiosis of the zygote, the spores formed are retained and germinate within the zygosporangium. Only the hyphae produced from one or more of these spores emerge from the zygosporangial wall. Many Zygomycetes also produce spores sexually (by mitotic divisions). These asexual spores are produced inside of a terminal cell at the tips of specific hyphae. The hyphae for most Zygomycetes are coenocytic and thus multinucleate. In lab today you will be observing two of the more common members of Zygomycetes, Rhizopus stolonifer or black bread mold, and Candida albicans. PART A: REPRODUCTION From the slide tray on your lab bench, obtain a prepared slide of R. nigricans (#3). Observe hyphae. Find and draw the different sporangia in the space below. Label them as to sexual or asexual structures. 1. Look at the Combination slide (Mold types at the front bench). Can you pick out the Rhizopus? (It also contains Aspergillium and Penicillium.) How is it different from the others?

4 4 4. Why are zygospores produced only if two compatible strains of Rhizopus are present? 5. Why are the terms "+" and "-" used instead of male and female? 6. Can you tell if the hyphae are aseptate or septate? Which should they be? 7. Which spores you observed in Part A were the result of meiosis? Meiosis? Can you tell them apart based on appearance? 8. Rhizopus often grows on materials that are predominately made of insoluble starch (such as bread). How does it obtain its food? 9. How does the zygosporangium differ in appearance from the asexual sporangium? 10. Is the ploidy of the spores produced in the zygosporangium the same as the ploidy of the asexual spores? Can you tell by looking at them? Explain. 11. Examine the slide of Candida albicans (#4). What differences do you see between Candida and Rhizopus? EXERCISE 2: MYCORRHIZA and the GLOMEROMYCETES/ GLOMEROMYCOTA Mycorrhiza is a mutualistic association between fungi and plants. In fact, mycorrhiza means fungus roots. These associations occur in upwards of 80% of plants. They increase the surface area increasing the plants ability to capture water and nutrients. The fungus supplies the plant with nutrients from the soil environment and the plant supplies the fungus with a carbohydrate source. There are two major types of mycorrhiza: endomycorrhiza and ectomycorrhiza. Endomycorrhiza penetrate the root cells, and ectomycorrhiza surround root tissues. Endomycorrhiza are the most common of the two; members of the Glomeromycetes form endomycorrhiza or arbuscules (or arbuscular mycorrhiza). Ectomycorrhiza may be Ascomycetes, Basidiomycetes, and even Zygomycetes. Ectomycorrhiza are mostly found on

5 woody species such as beeches, oaks, willows, and pines. In addition, ectomycorrhizal species often form fruiting bodies such as truffles and various species of Amanita. We will examine both an endomycorrhizal and an ectomycorrhizal species in lab. The Class Glomeromycetes derives its name from the type genus Glomus rather than any reproductive structure. Glomeromycetes form arbuscules with about 80% of vascular plants. Its hyphae are mostly coenocytic. Asexual reproduction occurs by multinucleate spores with the host plant cells. Most Glomeromycetes cannot survive without the host plant. Obtain the slides labeled endomycorrhiza (#16) and ectomychoohiza (#17) and examine them. 12. What differences do you see between the two types of fungi? 5 EXERCISE 3: ASCOMYCETES/ ASCOMYCOTA The Class Ascomycetes derives its name from the sac-like sporangium called an ascus (plural, asci). The asci form at the end of dikaryotic hyphae on the outer surface of the fruiting body. The two nuclei contained within an ascus fuse to form a zygote. The zygote undergoes meiosis to form four ascospores. The ascospores may then undergo mitosis producing 8 or 16 ascospores. Many ascomycetes reproduce asexually by the production of conidial spores. Hyphae of most Ascomycetes have septa with perforations although some Ascomycetes may be coenocytic. Ascomycetes that you will observe in lab today are Aspergillus sp., Penicillium sp., the single-celled yeast Saccharomyces cerevisiae, the multicellular cup fungi, Peziza sp., Sordaria fimicola, and morels, Morchella sp. PART A: Saccharomyces cerevisiae Saccharomyces cerevisiae (baker's yeast) is a unicellular member of the Ascomycetes. It usually reproduces asexually by a process called budding. During budding cells divide mitotically with the smaller "new" cells appearing to be pinched off of the larger "parent" cell. From the labeled container at the front of the room, obtain a drop of S. cerevisiae and put it on a slide and add a cover slip. Observe the drop under the microscope. (Remember: For clear, unstained specimens, decrease the light coming through the iris diaphragm.) As you focus up and down it should appear as though there are many layers of yeast cells. Budding cells are usually found in top "layer." From the slide tray on your lab bench obtain a prepared slide of Saccharomyces sp. (#5). Observe the ascospores. PART B: PEZIZA sp. Obtain a prepared slide of Peziza (cup fungus) (#6) from the slide tray on your lab bench. Before placing it on the microscope stage, look at the slide with the dissecting microscope. Are there structures that you should look for? After placing the slide under the microscope, observe the hypha. Then look for spores in the specimen.

6 6 13. Are the spores produced in or on any particular structure? What does this structure look like? 14. Could you tell if the hyphae were aseptate or septate? Which should they be? PART C: SORDARIA sp. Obtain a prepared slide of Sordaria (cup fungus) (#7) from the slide tray on your lab bench. Before placing it on the microscope stage, hold the slide up to the light and note the shape of the specimen. Make sure that you examine the full length of the tissue on the slide. After placing the slide under the microscope, observe the hypha. Then look for spores in the specimen. 15. Are the spores produced in or on any particular structure? What does this structure look like? Is it the same type of structure that you saw in Peziza? 16. Why are Ascomycetes referred to as cup fungi? PART D: Morchella In a jar at the front or side bench of the lab is a large bottle labeled Morchella with some fungal fruiting bodies preserved in it. These are morels, highly prized for their delicate flavor. Without opening the jar look at the structures. 17. After looking at slide #8, what fungal phylum do you think these fungi belong to? Why? (and don t say because it s in this section!) 18. Name 3 specific microscopic structures you would look for to determine if you are correct. 19. When looking at slide #8, how many of those structures do you see? Which ones?

7 7 20. The fruiting body of the Morchella looks very much like a Mushroom. Why is it not classified as a Basidiomycetes? PART E: CONIDIAL FUNGI: Penicillium and Aspergillus The classification of the fungi is based on the morphology of specific structures involved in sexual reproduction. Nevertheless, the sexual life cycle of many fungi have not been observed. These fungi are grouped together in a form class or form phylum in the Conidial Fungi or the group known as Deuteromycetes. Molecular analysis has identified almost all of these as Ascomycetes. The genera Penicillium and Aspergillus are sometimes placed with the ascomycetes and other times are split between the ascomycetes and Conidial Fungi. Sexual reproduction by the production of ascospores is known in a number of species. However, reproduction is primarily done asexually by the production of conidia. Using the Aspergillus slide in the slide tray at your lab bench (#9), note the arrangement of the spores. See if you can pick out the Aspergillus from the combination slide (at the front bench) as well. do the same for the Penicillium slide (# 10) 21. How does the appearance of the spores of Penicillium and Aspergillus differ from the spores of Rhizopus? 22. Penicillium cultures are usually bluish-green and Aspergillus cultures are typically brownishblack. Can you tell the color on the prepared slides? Why or why not? What part of the fungus would you guess would give the culture its color? EXERCISE 4: BASIDIOMYCETES/BASIDIOMYCETES The Class Basidiomycetes derives its name from the club-shaped sporangium, the basidium. The basidium is the terminal cell of the dikaryotic hyphae that form part of the gill surface of the mushroom. Fertilization and meiosis occur inside of the basidium. Each of the four nuclei formed by meiosis migrates into one of four club-like projections at the tip of the basidia. Basidia are found in the fruiting body on gills, teeth, or inside pores. These four projections on the tip of the basidium form the basidiospores. Asexual reproduction may be by conidia, budding, or fragmentation. The hyphae of Basidiomycetes are septate with elaborate structures bordering the perforation. The dikaryotic hyphae have an elaborate mechanism for cell division called a clamp connection. The clamp connection is unique to this phylum; but there is an analog in Ascomycetes called the crozier. There are two unusual groups within Basidiomycetes: the rusts and the smuts. These fungi do not have obvious fruiting bodies like the majority of the group, but they do produce their

8 8 spores on a basidium. They have very complex life cycles (often involving more than one host) and are economically important plant pathogens. Basidiomycetes that you will examine today in lab include Coprinus, Cronartium (a rust), Ustilago (a smut), and several dried specimens of pored, gilled, and toothed fungi. PART A: Agaricus sp. Observe the mushrooms at the front or side bench of the class. These are Agaricus species, the common cultivated mushroom. The bulk of this fungus was left back at the mushroom farm where it grew on rich organic compost. The mushroom structure that we eat is a fruiting body that was produced by the hyphae at the farm. On the lower surface of the fruiting body are spore-bearing surfaces called gills. Your lab instructor will give you a portion of a mushroom. Using forceps pull off a portion of a single gill. Make a wet mount of the gill and look for spores. In addition to the white button mushroom, there are several other live and dried specimens. Examine them under both the dissecting nd compound microscopes. 23. Are all the dried fungi Basidiomycetes? How can you tell? 24. Do the basidia look different between the gilled, pored, and toothed fungi? In what way? 25. Would it surprise you to find out that the Portobello and the Button mushroom are the same species? Why? What characters might you look at to test that hypothesis? 26. There are two species of Agaricus that are commonly consumed: Agaricus bisporus and A. brunnescens. Agaricus bisporus has only 2 spores per basidium instead of the normal 4. Which species do you have? PART B: COPRINUS SP. Obtain the slide labeled Coprinus sp. (#11) 27. There are two types of hyphae that make up the fruiting body. What is their ploidy and what is their origin?

9 9 PART C: RUSTS FUNGI AS PATHOGENS Cronartium, a rust, is a fungal disease that typically attacks pines and a member of the flowering plants. This rust is in the phylum Basidiomycetes. It has a very complex life cycle, producing multiple different types of spores and involving 2 host plants, pine and (for C. ribicola) members of the genus Ribes. Examine the prepared slides of the different stages in the life cycle of Cronartium (slides #12-14). 28. Find (from your text, the Color Atlas, or the Internet) and draw the life cycle of this rust in the space below. Use whatever resources you need, but please cite them! 29. How different do the different structures in Cronartium look from one another? PART D: SMUTS FUNGI AS PATHOGENS Ustilago, a smutt, is a fungal disease that typically attacks corn. It is in the phylum Basidiomycetes. The life cycle of smuts is very similar to the average Basidiomycete, but it does not have a obvious fruiting body. It does, however, have a very characteristic morphology. Examine the prepared slide of Ustilago (slide #15). 30. Does Ustilago look like any of the other Basidiomycetes that you ve seen? EXERCISE 4: SLIME MOLDS Slime molds are distinct from fungi; they form spores, but they lack cell walls and are classified based on whether they are plasmodial (Myxomycota) or cellular (Myxamoeba). We will look at an example of each: Dictyostelium and Physarum. A plasmodial slime mold exists in a multi-nucleate amoeboid-like organism until environmental cues cause aggregation of the protoplasm and the formation of fruiting bodies. The plasmodial slime mold, Physarum. has a yellow, fan-shaped plasmodium. They are particularly fond of oats. When habitats become unfavorable, the plasmodium encysts into a sclerotinum.

10 10 The cellular slime mold, Dictyostelium, is the model organism for studying the development of multicellularity as these organisms can behave as single-celled organisms, colonial organisms, and multicellular organisms depending on the stage during their life cycle when they are being observed. Aggregation, driven by cyclic AMP 31. Examine the Physarum slide (#20) and compare it to the live material. So you see similar structures in both cases? EXERCISE 5: LICHENS When two different types of organisms live in a very close association, their relationship is described as symbiotic. A symbiotic relationship typically involves the transfer of material directly between the cohabitants. Often one of the organisms lives inside of the other. If the relationship between the organisms benefits both of them the symbiosis is said to be mutualistic. When the relationship is beneficial to one and harmful to the other the relationship is parasitic. A relationship in which one symbiont is benefitted and the other derives no apparent harm or benefit is commensalistic. Lichens are a controlled parasitic symbiotic relationship between a heterotrophic fungus (usually an ascomycete) and a photosynthetic organism (either a green alga or cyanobacteria, or both). Metabolically the fungus benefits greatly in this relationship. Its hyphae surround the outside surface and even penetrate the algal cells. The fungus absorbs various sugar alcohols, glucose, and vitamins from the algal cells. The algal cells are metabolically independent of the fungus and grow faster when they are unconstrained by the fungus. Together the two organisms of the lichen form a single spongy body called a thallus (thalli, plural). The thallus is composed primarily of the fungus with the algae/cyanobacteria comprising only 3-7% of the thallus volume. The fungal hyphae form compact upper and lower layers with a loose hyphal network in the middle. The algal component of the lichen is located just below the upper hyphal layer. The thallus lacks any water tight covering and changes shape and texture relative to moisture availability. In a moistened condition, lichen respiration and photosynthesis reach their peak. When the thallus dries out it becomes brittle and metabolism reduces significantly, almost to nothing. Much of the time lichens are dried and metabolic activity is at a minimum. Because of this lichens grow at a pace of only 0.1 mm to 1 cm per year. The complexity of the lichens goes beyond the simple idea of unrelated organisms living together. The different shapes and forms of the lichen occur because there are many different fungi and a few different algae that make up the thallus. Most of the fungi are ascomycetes and a few are basidiomycetes. In some situations the fungal component contains more than one species. The combination of fungal species with different algae/cyanobacteria results in the different shapes and colors of the lichens. A few lichens have both a green alga in the lower portion of the thallus and a cyanobacteria in the upper thallus. In these situations the lichen is composed of organisms from three different kingdoms. Even though the gross morphology of lichens is useful in identification, secondary chemical compounds produced mostly by the fungus are used in the determination of lichen species. There are approximately 13,500 species of lichens named.

11 Lichens reproduce asexually by fragmentation and the production of specialized propagules. Almost any part of the lichen can break away from the thallus and grow into a new lichen as long as both organisms are present in the fragment. On the upper surface of the lichen are openings where small masses of hyphae attached to algal cells will erupt. These specialized propagules, called soredia, may be washed or blown to a suitable habitat and grow into a new lichen. Even though the fungus of the lichen may go through sexual reproduction, the spores are generally released without algal cells attached. Under controlled conditions in lab these spores can recapture certain algal species to form a new lichen. However, this process, "lichenization" has not been observed in nature. Lichens are distributed in almost all terrestrial and some aquatic habitats around the world. They can withstand extremes in temperatures and moisture and survive exposed on desert rocks and on frigid substrates of the polar regions. Lichens play an important role in primary plant succession on bare rock where the acids produced by the fungus help breakdown the rock into its mineral components. Lichens may also be an important link in some food chains. Grazing animals such as reindeer, caribou, slugs, snails, and some insects ingest lichens. PART A: LICHEN STRUCTURE Secure a prepared slide of Physcia (# 18-19). As you observe the specimen, look for the hyphae and the algal cells. Also look for the ascocarp and note the ascospores located in the asci. PART B: After you have observed this prepared slide, obtain a small piece of fresh lichen from your lab instructor. Place this on a slide and use dissecting needles to pull the lichen apart as much as possible. You may need to use a razor blade to cut several thin sections of the thallus first. Make a wet mount of your specimen. 32. Is the algae of the lichen located in the upper middle or low portion of the thallus? What accounts for the greenish-gray color of many lichens? 34. Do you see a color difference in fresh lichen versus older lichens? What might cause that? PART C: LICHEN GROWTH FORMS At the front or side of the lab are a number of specimens of lichens, separated by growth form. After observing these specimens, describe each of the growth forms. a. Crustose: b. Foliose:

12 12 c. Fruticose: 35. While you where looking at the lichens, did you notice any structure that identified the mycobiont as an ascomycete? A basidiomycete? What were they? What about the photobiont? Could you tell if it was a prokeryotic or a eukaryotic species? 36. Label diagram below.

13 13 Throughout this lab exercise, you will see life cycle diagrams and a diagram of a generic lichen. In the blanks labeled "S" write the name of the structure indicated and its ploidy. In blanks labeled "P" write the process which has just occurred. 37. LIFE CYCLE: Allomyces arbusculus PHYLUM MEIOSIS TYPE GAMETE TYPE

14 LIFE CYCLE: Rhizopus stolonifer PHYLUM MEIOSIS TYPE GAMETE TYPE

15 LIFE CYCLE: Peziza sp. PHYLUM MEIOSIS TYPE GAMETE TYPE 40. LIFE CYCLE: Sordaria sp. PHYLUM MEIOSIS TYPE GAMETE TYPE

16 LIFE CYCLE: Coprinus sp. PHYLUM MEIOSIS TYPE GAMETE TYPE

17 17 TERMINOLOGY TO BE FAMILIAR WITH 1. alternate host 2. ascocarp 3. Ascomycetes 4. ascospore 5. ascus/asci 6. asexual 7. basidiocarp 8. Basidiomycetes 9. basidiospore 10. basidium/basidia 11. budding 12. chitin 13. clamp connection 14. coenocytic 15. conidia 16. Conidial Fungi 17. crustose 18. commensalistic 19. dikaryotic 20. extra cellular digestion 21. fertilization 22. foliose 23. fruticose 24. gametangium 25. gametes 26. gills 27. glycogen 28. haploid 29. hypha/hyphae 30. imperfect fungi 31. lichenization 32. mating type or strain 33. meiosis 34. multinucleate 35. mutualism/ mutualistic 36. mycelium 37. mycobiont 38. mycorrhiza a. endomycorrhiza b. ectomycorrhiza 39. parasite 40. perforate 41. phycobiont 42. rhizoid 43. rust 44. saprobe 45. septa or septate 46. sexual 47. soredia 48. sporangium 49. sporangiophore 50. spore 51. symbionts 52. symbiosis / symbiotic 53. thallus/ thalli 54. uninucleate 55. zygospore 56. Zygomycetes 57. zygosporangium 58. zygote 59. zygotic meiosis

18 18 QUESTIONS FOR FURTHER THOUGHT 1. What two cellular processes are necessary to complete a sexual life cycle? Where do these events occur in the life cycle of Rhizopus? In Peziza? In Agaricus? 2. Why is it so difficult to keep molds, such as Rhizopus or Penicillium, from growing on things like bread, fruit, etc? 3. You start to make a peanut butter sandwich but you notice there are small bluish clumps of mold growing on the bread. You pinch off the mold and then make your sandwich. Have you gotten rid of the mold on the bread? Why or why not? 4. Why is the term "imperfect" used to describe the Conidial Fungi? 5. In the life cycles of the fungi the terms "+ strain" and "- strain" are used instead of male and female. Why? 6. What is the ecological role of the fungi? 7. What foodstuffs are produced with the aid of living fungi? 8. What evidence is given in the textbook that support the idea that the fungus is parasitic upon the algae? 9. What are the commercial uses of lichens? 10. What is the ecological role of lichens? 11. In what habitats do lichens grow? 12. Some of the rock tripe lichens in the Smoky Mountains have been measured at 1 meter across. If they grow at a maximum rate of 1 cm per year, how old are they? 13. Are lichens autotrophic or heterotrophic? 14. Make a list of some fungi that have economic importance and what that importance is. 15. What factors account for the very rapid growth rates of yeast cultures (in test tubes or in bread dough)? 16. What metabolic process is the yeast undergoing that causes bread to rise? What is the gas produced? 17. Are the spores in the ascus a result of sexual or asexual reproduction? What about the spores on a basidium?

19 What are other crop diseases are caused by rusts and smuts? How many hosts does each one have? 19. Do fungi cause disease or illness in animals or humans? Give some examples. Are there any rusts and/or smuts that infect animals?