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6. FUNGI
INTRODUCTION
The Kingdom Fungi includes a diversity of organisms that all have certain traits in common. They are heterotrophic (consumers) obtaining their nutrients by absorption. They digest their food outside of their bodies and then absorb the digested products into their cells. Some are decomposers , feeding on dead and decaying material. Some fungi are predators , capturing and killing their prey (nematodes for example). Other fungi are parasites , living off of another organism without killing the host (ringworm is really a fungus on your skin). Still others form mutualistic associations with plant roots; these fungal/root associations are called mycorrhizas. Through this relationship fungi contribute to plant growth and survival by obtaining nutrients and water through a vast array of hyphae.
Fungal bodies are made of thread-like structures called hyphae that grow through the growth media - dead wood, leaf mold, soil, skin, glass, etc. Each cell is surrounded by a cell wall made up of a carbohydrate called chitin. A mass of hyphae is called mycelium. When the fungus is ready to reproduce it will produce spores either sexually or asexually. We usually only notice the fungus when it reproduces because the individual hyphae are too small to see with the naked eye, but the structures that hold the spores are larger and more obvious. Those fungi that reproduce asexually have spore-producing structures called sporangia. In the fungi that reproduce sexually we call the spore-producing structure a fruiting body (like a mushroom), or in the case of the Zygote fungi it is also called a sporangium.
Here is a review of the basic classification system used for all living organisms:
Type of Cell Domain Kingdom Example Prokaryotic Archaea Not Used Prokaryotic organisms found in extreme environments Prokaryotic Bacteria Not Used common bacteria, cyanobacteria Eukaryotic Eukarya Protists algae, Paramecium , Amoeba , Euglena Eukaryotic Eukarya Fungi mushrooms, mold, Penicillium Eukaryotic Eukarya Animals vertebrates, insects, nematodes, sponges Eukaryotic Eukarya Plants moss, ferns, redwoods, flowering plants
GOALS AND OBJECTIVES
- Know the distinguishing characteristics of the Fungi.
- Understand the life history of fungi. Know the function of hyphae, sporangia, fruiting bodies, and spores.
- Recognize and distinguish the Kingdom Fungi from organisms in other Kingdoms.
- Understand the differences between sexual and asexual reproduction, and the advantages and disadvantages of each.
- Be able to recognize the three phyla of the Kingdom Fungi.
- Understand the ecology and structures of lichens.
- Be able to identify the three different forms of lichens.
KINGDOM FUNGI CLASSIFICATION USED IN LAB
Fungi are divided into three phyla depending on their mode of reproduction.
PHYLUM ZYGOTE FUNGI – bread molds and other terrestrial molds Sexual reproduction begins with the fusion of two different types of hyphae and results in the formation of a resistant structure (a type of fruiting body) that produces a sporangium. This sporangium forms many spores with combined traits of each parent. Zygote Fungi also reproduce asexually by forming a sporangium that produces spores genetically identical to the original hyphae.
PHYLUM CLUB FUNGI – mushrooms, shelf fungi, puff balls, earthstars, and coral fungi Mushrooms are a familiar example of a fruiting body of the club fungi. Club Fungi sexually reproduce four spores on the surface of club-shaped structures called basidia.
PHYLUM SAC FUNGI – yeast, morels, truffles, Penicillium , and other blue-green molds Sexual Reproduction results in eight spores that are formed in sac-like structures called an ascus.
Rhizopus (compound microscope). Make illustrations of bread mold fungi as you see them.
Phylum: ________________ Objective Lens: __________ Total Magnification: ______
- Describe the shape of a hyphal filament.
- How does this shape allow for maximum nutrient acquisition?
- Hyphae elongate from the tip. How does this help them obtain nutrients from their environment?
Humidity and Fungal Growth
Consider the conditions under which fungi will grow. Do they require light, darkness, moisture?
- What are the requirements for fungal growth?
2.What rooms of your home are most likely to promote fungal growth?
3.There are fungi that infect human skin. What parts of the body are most likely to promote fungal growth?
Phylum – Club Fungi
Club fungi are the typical types of fungi that we think of as a mushroom. The fruiting bodies of the club fungi vary widely and are grouped by general characteristics such as the area or structure on which their spores are formed. For instance gill fungi are club fungi that reproduce on structures called gills. On these gills are minute club-like structures called basidia that produce spores. Gills Gill Fungi (A type of Club Fungi) Notice the gills on which the spores form.
Phylum – Sac Fungi.
Although the Sac Fungi are less familiar to most people this phylum is very important economically. Yeast is a sac fungus used to make bread, beer, and wine. Pencillium is a sac fungus that was the source of the first antibiotic and its close relatives are responsible for the flavor of cheeses such as Brie and Roquefort. Truffles and morels are sac fungi prized for flavor. Still others cause extensive economic damage as they cause crop diseases or food spoilage.
All sac fungi reproduce 8 spores in sac-like structures called asci.
Peziza cross-section (prepared slide).
Obtain a prepared slide of the cup fungus Peziza (cross section). A. Focus your microscope on the slide and locate the asci sacs along the upper layer. Notice that each mature asci sac contains 8 spores. B. Identify the asci sac and spores.
Lichens Lichens are a mutualistic relationship between a fungus and an alga. The fungus provides a protective environment for its photosynthetic algal partner. The fungus benefits by having a source of nutrients, which leak, from the algal cells.
There are three types of lichens: crustose, foliose, and fruticose. Crustose lichens form a crust-like layer on the surface of rocks or branches. It is almost impossible to separate a crustose lichen from its substratum. Foliose lichens appear as a leaf-like layer on the substratum. If it is possible to get a pin beneath the lichen it is foliose (not crustose). The third type is the fruticose lichen. Fruticose lichens hang from branches or are shrub-like. Since lichens absorb both water and minerals from the air they are sensitive to air pollution. An area with an abundance of lichens probably has good air quality.
Observation 10 – Lichen Examine the lichen specimens with your naked eye and then the dissecting microscope.
- What two organisms make up a lichen? What are their modes of nutrition (autotrophic or heterotrophic)? Organism Mode of Nutrition
- Which organism in a lichen produces a source of energy-rich nutrients that feeds the other?
- When two organisms live in close association, what term is applied to the relationship?
- What term applies when both benefit from the relationship?
- Name at least one ecological role of lichen in the environment.
Observation 12 – Types of Lichens.
Name three types of lichens and be able to identify each.
Fruticose Lichen
Oak leaves
Foliose Lichen
Lichen “Old Man’s Beard”
Crustose Lichen
