Chapter 2. DIVERSITY IV—FUNGI

Learning Objectives

Lab 12
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General Purpose

Conceptual

  • Be able to compare and contrast the major groups within the kingdom Fungi.
  • Be able to recognize and describe the structures important in fungi reproduction.

Procedural

  • Examine and draw species from each of the represented phyla.
  • Examine and draw reproductive structures from each of the represented phyla.
  • Do the online exercises that examine the diversity of fungi.

THERE WILL BE A NUMBER OF ONLINE EXERCISES AS PART OF THIS LAB, SO PLEASE BRING YOUR LAPTOP OR TABLET TO LAB IF POSSIBLE.

Exercise 1. Allomyces

Allomyces sp. is a member of Chytridiomycota. This is an aquatic fungus with flagellated zoospores and gametes.

PROCEDURE

  1. A culture of Allomyces sp. is available on the demonstration table. Examine the live specimen and make a sketch of the organism in your laboratory notebook.
  2. Answer the following question in your laboratory notebook: What is the food source for the Allomyces sp.?
  3. Examine a wet mount slide of Allomyces sp. with a compound microscope using the 4× and 40× lens. Find the reproductive structures, the bulb-like sporangia that give rise to spores. Observe the structure of the hyphae. Make sketches and notes of these observations in your laboratory notebook.

Exercise 2. Rhizopus

Rhizopus sp. is known as black bread mold and is a member of Zygomycota. Species in this phylum are primarily terrestrial and live on decaying matter. The zygomycetes reproduce with zygospores.

PROCEDURE

  1. Observe live sample of Rhizopus (black bread mold) using the dissecting scope. Keep dish covered.
  2. Examine the hyphae that form the mycelium on the surface of the agar or bread. Make a sketch and describe the appearance of the hyphae in your laboratory notebook.
  3. Locate the hyphae that grow upright from the surface and bear globular sporangia at their tips. Each sporangium contains hundreds of asexual spores. Make a sketch and label the hyphae and sporangia in your laboratory notebook.
  4. Rhizopus also reproduces sexually. Successful sexual reproduction requires that two compatible strains (“+” and “−”) fuse. Examine the culture dish on the demonstration table that was inoculated with both plus and minus strains of Rhizopus. Notice the zygotes formed where the hyphae came into contact that have fused during sexual reproduction. Make a sketch and label the hyphae and sporangia in your laboratory notebook.
  5. Examine the fixed slide of Rhizopus using a compound microscope. Look for the sexual reproductive structure of the zygospore. Make a sketch in your laboratory notebook and label the important features.
  6. Answer the following question in your laboratory notebook: How would cells produced by the zygote differ genetically from those produced in the asexual sporangia?

Exercise 3. Ascomycetes

PROCEDURE

  1. Examine the fruiting bodies of various Ascomycota that are on the demonstration table and make a sketch of several of the organisms in your laboratory notebook.
  2. Examine a specimen of Peziza, a cup fungus. The cup is composed of many hyphae packed tightly together—fungi never have true tissues, but are of hyphal construction. The cup contains many developing and mature asci not visible to the naked eye. Make a sketch of the organism in your laboratory notebook.
  3. Observe a prepared slide of Peziza, sectioned through the cup using a compound microscope. Notice the arrangement of the asci. Find some asci with eight spores inside. You may notice that the spores stain red and green in different asci, denoting differences in spore walls over time of development. Make a sketch of the important features in your laboratory notebook.
  4. Observe the mycelium of the Sordaria culture on demonstration. Do not open this culture. Make a sketch of the organism in your laboratory notebook.
  5. Obtain a demonstration slide of Sordaria fruiting bodies known as perithecia (singular perithecium) from your laboratory instructor. The perithecia are structures in which asci form. Observe the slide using a compound microscope. Note the asci with all eight spores. Make a sketch of the important features in your laboratory notebook.
  6. Answer the following questions in your laboratory notebook: Is there any difference in the color of the ascospores? Are there variations in the arrangement of ascospores in different asci? Why does this happen?
  7. Observe the culture plate of Penicillium that reproduces asexually by the formation of green conidia (singular conidium) at the tips of the modified hyphae called conidiophores. Make a sketch of the organism in your laboratory notebook.
  8. Prepare a wet mount from a suspension of Penicillium conidia provided by your instructor. Observe the slide using a compound microscope. Make a sketch of the important features in your laboratory notebook.
  9. Answer the following question in your laboratory notebook: What is the relative size of the conidia?
  10. View the stained fixed slide of Penicillium conidia using a compound microscope. Make a sketch of the important features in your laboratory notebook.

Exercise 4. Basidiomycetes

PROCEDURE

  1. Examine the fruiting bodies of various Basidiomycota that are on the demonstration table. Note the diversity of structures in the fruiting bodies. Make a sketch of several of the organisms in your laboratory notebook.
  2. Using a dissecting microscope, examine an edible mushroom and notice the many gills on the lower surface of the umbrella-shaped cap. Basidia line the gills. Make a sketch of the important features in your laboratory notebook.
  3. Using a compound microscope examine a prepared slide of a cross section through the cap of a mature Coprinus, a common mushroom that grows on dead wood and dung of herbivores. Locate the hyphae, basidia, and basidiospores. Make a sketch of the important features in your laboratory notebook.

Fungal Forms with Unique Lifestyles

Certain ways of living that involve both morphological and ecological specialization have evolved independently among the zygomycetes, the ascomycetes, and the basidiomycetes. These lifestyles allow the fungi to take advantage of unusual habitats.

Exercise 5. Molds

PROCEDURE

Examples of molds and cheeses are on display on the demonstration table. Note any diversity. Make a sketch of the important features in your laboratory notebook.

Exercise 6. Yeasts

PROCEDURE

  1. Using a compound microscope examine the demonstration slide of a wet mount of yeast cells. Use the high power objective (40×) to observe the cells. Look for some examples of the cells budding. Make a sketch of a few cells with buds in your laboratory notebook and label the buds.
  2. Answer the following question in your laboratory notebook: What type of reproductive pattern (sexual or asexual) is the budding of yeast?
  3. View economically and biologically important products made with yeast.

Exercise 7. Parasitic Fungi—I

PROCEDURE

  1. Look on the internet for examples of Cordyceps species. These fungi are ascomycetes that attack arthropods in the class Insecta. There are hundreds of species of Cordyceps, each which infects a different insect host.

Exercise 8. Parasitic Fungi—II

PROCEDURE

  1. Examine the specimens of leaf spot on display on the demonstration table. Make a sketch of the important features in your laboratory notebook.
  2. Place a leaf on a slide (don’t use a coverslip). Examine the specimen with a compound microscope using the 4× and 10× lens. Make a sketch of the important features in your laboratory notebook.
  3. Answer the following question in your laboratory notebook: What structures would indicate the presence of a fungal infection?

Exercise 9. Mutualistic Symbionts—Lichens

Lichens are mutualistic symbiotic partnerships formed between fungi (usually ascomycota) and photosynthetic organisms (chlorophyta or cyanobacteria).

PROCEDURE

  1. Examine the lichen specimens that are on display on the demonstration table. Make a sketch of the important features in your laboratory notebook.
  2. Try to recognize the many lichens on trees as you leave lab.

Exercise 10. Mutualistic Symbionts—Mycorrhizae

Mycorrhizae are mutualistic associations between fungi and the roots of most vascular plants.

PROCEDURE

  1. Examine the images of mycorrhizae on the roots of vascular plants. Make a sketch of the important features in your laboratory notebook.
  2. Examine a mixed slide of root tip in symbiotic relationship with a mycorrhizal fungus with a compound microscope using the 4× and 10× lens. Find the red stained mycorrhizal hyphae in and around the root tip. Make a sketch of the important features in your laboratory notebook.
  3. Answer the following questions in your laboratory notebook: With which plants are these mycorrhizae associating? How could you distinguish if these mycorrhizae were zygomycetes, ascomycetes, or basidiomycetes using a microscope?