SLIDE 1: Attributes of Fungi.
This is the master slide for the slide presentation and it will appear several times. The lecture will focus on these six points. As the saying goes, "redundancy is the mother of learning."
SLIDE 2: Attributes of Fungi. "Evolutionary Relationships" is bold; the other attributes are faded.
This slide sets the general pattern for the style of the presentation. The slides following the highlighted attribute will focus on that attribute.
SLIDE 3: Evolutionary Relationships of Fungi.
The major points on this slide should be enough for non-majors. Probably the most important point is that "Fungi are not 'simple plants.'"
Stress differences between plants and fungi. I.e., both plants and fungi have walls, but the walls of plants contain cellulose (which fungi do not have) and the analogous structure role in the walls of fungi is played by chitin (which plants do not have). To make the point, one may mention that some animals do synthesize and accumulate chitin.
Whereas it is true that no fungus is flagellated, sperm of many plants are flagellated, sometimes to extraordinary degrees.
SLIDE 4: Phylogenetic relationship among organisms.
It is important for students to know that plants, animals, and fungi certainly do not represent the diversity on earth. Perhaps with a broad sweeping hand, indicate that most of the area on this chart is devoted to organisms that lack a nucleus; with a second broad sweeping hand, indicate that many nucleus-containing cells are too simple or too different to be considered as plants, animals, or fungi. Finally, fungi, animals, and plants represent separate evolutionary pinnacles.
SLIDE 5: Attributes of Fungi. "Body Plan" is bold; the other attributes are faded.
Again, this slide will appear each time to separate the foci and attract attention to the discussed attribute.
SLIDE 6: Body Plan of Fungi.
One may consider drawing a filament on the black board to drive the point home. As an aside, because it will come up later, the cell wall between adjacent cells in some fungal taxa is absent (meaning, really, that the organism is not cellular in strict sense of the word.)
This slide leads into the next concept (Nutrition), so stress that no part of the mycelium is very far away from the substance in which it is growing. Said differently, fungi have a large surface area-to-volume ratio, which allows them to penetrate large volumes of the substrate at a minimum cost.
Of course, any broad sweeping statement that one makes has exceptions. Yeasts are not filamentous (but some are dimorphic and can convert to a filamentous form under the right circumstances.) Importantly, this exception does not detract from the functionality of the body-plan statement ("All parts of the nutrient-acquiring portions of a fungus are in close proximity to the substrate.")
SLIDE 7: Attributes of Fungi. "Mode of Nutrition" is bold;
the other attributes are faded.
SLIDE 8: Nutritional Mode.
Animals ingest chunks of food, which is digested "inside" their bodies; plants make food from simple chemicals and the energy in sunlight. A fungus, like your GI tract, secretes enzymes, which break the complex molecules down to allow for absorption of the monomers or simpler fragments.
SLIDE 9: Attributes of Fungi. "Sexual Reproduction" is bold;
the other attributes are faded.
SLIDE 10: Sexual Reproduction.
Perhaps the last statement deserves emphasis first. Many fungi reproduce exclusively by asexual means-always involving the formation of a haploid spore by mitosis.
It would require too much time to develop the concepts of life cycles, such as plant-invariant alternation of generations in any detail. However, most students will know from the previous units on genetics that animals and plants derive traits from parents in a virtually equal way. I.e., haploid gametes combine to form the diploid, which is the familiar organism. Fungi are different in that the only diploid cell is the zygote. The zygote may go into dormancy, or it may divide meiotically right away. In any case, the generality is that a fungus is haploid.
(Like any simple generality, this statement can be challenged. A few fungi grow as a diploid, and in primitive plants (such as mosses) the haploid phase is the dominant one. However, unless you are challenged, I would suggest that you not clutter your lecture with these details. It is simply not possible to give a coherent lecture at this level and address exceptions.)
SLIDE 11: Attributes of Fungi. "Classification and Examples" is bold; the other attributes are faded.
SLIDE 12: Classification by Sexual Reproduction.
I suggest that you make a statement concerning the detail that you expect students to know about sexual reproduction and the three taxa of fungi.
This first rendition of the slide can be used as an overview: (a) There are three different kinds of fungi. The Zygomycetes are different from the other two, which share similarities. (b) The hypha of Zygomycetes is not cut into cells, except where the reproductive structures form. The larger black dots in the Zygomycete hyphae are nuclei. (c) In Zygomycetes, several zygotes form within the zygosporangium; each of these zygotes ("zygospores") can remain dormant until a proper condition exists for them to grow, when they "germinate" and form haploid spores, which "germinate" . . . . (d) Ascomycetes and basidiomycetes reproduce in a generally similar way, but they can be distinguished on the basis of the different types of sexual reproductive structures, the ascus ("cup"), and the basidium ("club").
I do not think that the simple scheme that I have given needs to be amplified on, but, in order to answer questions, I mention that some mycologists now consider chytrids to be fungi because of new molecular phylogenies. Years ago, many heterotrophic protists (chytrids, oomycetes, and the cellular and acellular slime molds) were classified as fungi, but that position is no longer tenable.
Overall, reproduction in fungi can be exceedingly complex, and I doubt that non-majors would be interested in the details. However, they should appreciate outcomes. E.g., one wheat stem rust of wheat requires that one phase of the life cycle is completed on wheat and the alternate phase is completed on the barberry bush. Knowledge of this fact suggested a non-toxic strategy for eradication of this wheat disease (viz., elimination of the barberry). Similarly, we can eliminate cedar-apple rust by clearing areas near orchards of cedar. This list goes on.
SLIDE 13: Classification by Sexual Reproduction. "Zygomycete" is bold; the other taxa are faded.
This slide is intended to shift the emphasis to Zygomycetes.
SLIDE 14: Example Zygosporangia of Rhizopus nigricans (bread mold) in various stages of development.At 3 o'clock, a zygosporangium has opened to release zygospores. In the center of the slide, some hyphae have recently become appressed and the gametangia are separated by walls from the remainder of the mycelium. At 7 o'clock, hyphae have apparently just fused.
SLIDE 15: Example Mucor on summer squash. North Leon County). Mucor is a relative of Rhizopus stolonifera (black bread mold), which is the name species for this taxon. The black dots are asexual sporangia with many, many spores inside [Possibly, this fungus is Chaonephora or Rhizopus-all of these fungi attack fruits and are indistinguishable at the level of information shown in this slide.]
SLIDE 16: Classification by Sexual Reproduction. "Ascomycete" is bold; the other taxa are faded.
SLIDE 17: Example Asci of Peziza sp. Ascomycetes and Basidiomycetes reproduce in similar ways-in both taxa, hyphae of (usually) different strains fuse and the resulting sexual-phase mycelium contains two (usually) genetically dissimilar haploid nuclei. The mycelium continues to grow; mechanisms have evolved to allocate faithfully the correct two nuclei to each daughter cell. At some time later, pairs of the nuclei fuse and form zygotes, which soon divide meiotically. In Ascomycetes, the four resulting haploid daughter cells usually divide mitotically to give a total of 8 haploid ascospores within a specialized sexual structure, the ascus.
SLIDE 18: Example Unidentified Ascomycete (North Leon County). This fungus apparently is not among the common ones as it is absent from available guide books and could not be identified by a local professional with mycology interests and experience.The asci-crowded together as you saw on the previous slide-line the upper surface of the cup-like fruiting body. The fruiting body, of course, is only a small fraction of the fungus, which is mostly underground.
SLIDE 19: Example Xylaria sp. (Birdsong, South Georgia). The asci line flask-shaped structures on the fruiting bodies. Found growing on wood, hence the name.
SLIDE 21: Classification by Sexual Reproduction. "Basidiomycete" is bold; the other taxa are faded.
SLIDE 22: Example Basidia of Coprinus pileus. The center of the slide shows four basidiospores connected to a basidium. Other basidia line the surface, and new basidiospores are developing at left.
SLIDE 23: Example Amanita sp. (cokerii?) White amanita. (North Leon County). Avoid amanitas unless you are an expert. Many are lethally poisonous and there is no known antidote. Ingestion of amanitas account for about 90 % of fatalities associated with eating collected mushrooms. The bold mushroom eater is fine for 12-36 hours, then gets sick (bloody diarrhea and so forth), recovers for some time, up to a day or two, then dies. But there are many kinds of mushroom poisons and it is hard to predict what the outcome of eating an unknown mushroom may be (individual idiosyncracies, age, synergy with alcohol consumption). Not to despair, all mushrooms are edible (but I should add that some are edible only once by any particular person).
SLIDE 24: Example Coral mushroom in the family Clavariaceae; could be one of several genera. (Birdsong, South Georgia).
SLIDE 25: Example Strobilomyces floccopus ("Old man of the woods," North Leon County).
SLIDE 26: Example Geastrum sp. ("Earthstar," North Leon County).
SLIDE 27: Example Phallus ravenelii ("Ravenel's stinkhorn," North Leon County).
SLIDE 28: Example Clathrus columnatus ("Columned stinkhorn," North Leon County).
SLIDE 29: Attributes of Fungi. "Role in the Biosphere" is bold; the other attributes are faded.
SLIDE 30: Role in the Biosphere.
Although we will return to these general roles in subsequent slides, I would suggest briefly going over them altogether at least once.
SLIDE 31: Role in the Biosphere. "Parasites" is highlighted; other roles are faded.
SLIDE 32: Example Toe-nail fungus-could be any one of a number of genera (undisclosed location). Many fungi are parasitic on man. These range from asymtomatic to merely annoying to genuinely irritating to lethal ones, particularly among immuno-compromised patients. Often, the lung is the site of a primary entry point for the pathogen. Interestingly, some human fungal parasites are opportunistic; i.e., they normally grow as saprobes in soil. When inhaled, they become parasites.
SLIDE 33: Example Podosphaera leucotricha ("powdery mildew," on Granny Smith apple. North Leon County). One notes the characteristically curled leaves.
SLIDE 34: Example Botryosphaeria dothidea = B. berengeriana = Physalospora piricola; anamorph=Fusicoccum aesculi, "apple ring rot," on Adina apple. North Leon County).
SLIDE 35: Example Diaporthe perniciosa= D. eres; anamorph=Phomopsis mali, "Phomopsis fruit decay," on Anna apple. North Leon County).
SLIDE 36: Example Cercosporella rubi, ("rosette," "double blossom," witches broom," on Shawnee blackberry. North Leon County).
SLIDE 37: Role in the Biosphere. "Saprobes" is highlighted; other roles are faded.
SLIDE 38: Example Pycnoporus cinnabarinus ("Cinnabar polypore" growing on Quercus nigra (water oak) in North Leon County.) Several different examples of saprophytic fungi will probably come to mind, so I did not extend this list. Three common esculents are cultivated as saprobes (the "ordinary" culinary mushroom and shitakes (both Agaricus) and oyster or shelf mushroom (Pleurotus sp.)
SLIDE 39: Role in the Biosphere. "Symbionts" is highlighted; other roles are faded.
SLIDE 40: Example Endomycorrhizal fungus (almost certainly a Zygomycete, but identification unknown) growing within the root cells of Asimina triloba (pawpaw). (North Leon County). An underappreciated fact is that most plants-about 80 %-form a symbiotic relationship with root fungi. Some plants have an obligatory requirement for the fungus, whereas others simply benefit greatly (by, e.g., enhancing PO4 acquisiton by 5x). In brief, the fungus gathers nutrients (particularly, as noted, PO4) and in return, the plant provides nutrition to the fungus. The relationship may be promiscuous, or there may be a high degree of specificity in the relationship. As a general rule, when you see mushrooms, you can be pretty sure that the unseen mycelium underground is associated with a plant.
This specimen has been stained so that the fungus is blue and the root appears in the background. The morphology shown here is common, but various types of mycorrhizae are found.
1 Thanks to K. Riddle for assistance with microphotography, H. He for photography, D. Chellemi and W. Petty for identification, and A. Lumsden, who assisted in a variety of ways.