I. Brief Introduction to the Kingdom Fungi
II. Generalized Life Cycle of Fungi
III. Human-fungus Interactions
BRIEF INTRODUCTION TO THE KINGDOM FUNGI
The Kingdom Fungi is an ensemble of diverse species. Current evidence suggests that all fungal species are not derived from a single common ancestor, consequently the Fungi are polyphyletic (multiple genealogies or lineages).
I. COMMON CHARACTERISTICS OF FUNGI
1. Heterotrophy - 'other food'. There are three major categories of heterotrophs, which include the saprophytes, symbionts, and parasites. Saprophytes (feed on dead tissues or organic waste); symbionts (mutually beneficial relationship between a fungus and another organism); parasites (feeding on living tissue of a host). Parasites that cause disease are called pathogens. Some parasites are obligate parasites (require a living host to survive), while others are facultative or nonobligate parasites (do not require a living host in order to survive).
2. Body form
Below: The sclerotium of Wolfiporia cocos or "tuckahoe" - the sclerotium is broken in two parts with a diameter of about 6 inches. Dug up from a flower bed near Jonesboro, AR. Photograph by M. Huss.
3. Fungus is often hidden from view. It grows through its food source (substratum), excretes extracellular digestive enzymes, and absorbs dissolved food.
4. Indeterminate growth.
5. Spores - asexual (product of mitosis) or sexual (product of meiosis) in origin.
Purpose of Spores
(a) Allows the fungus to move to new food source.
6. Vegetative phase of fungus is generally sedentary.
7. Cell wall present, composed of cellulose and/or chitin.
8. Food storage - generally in the form of lipids and glycogen.
9. Eukaryotes - true nucleus and other organelles present.
10. All fungi require water and oxygen (no obligate anaerobes).
11. Fungi grow in almost every habitat imaginable, as long as there is some type of organic matter present and the environment is not too extreme.
12. Diverse group, number of described species is about 69,000 (estimated 1.5 million species total).
II. LIFE CYCLE OF A 'TYPICAL' FUNGUS
Generalized Life Cycle of Fungi
REFER TO DIAGRAM FROM CLASS NOTES OR TO THE FOLLOWING:
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Some fungi produce spores or other modified cells to reproduce sexually (perfect stage or the teleomorph), others to reproduce asexually (imperfect state or the anamorp), and some species are capable of reproducing both ways (holomorph).
III. HUMAN-FUNGUS INTERACTIONS
Beneficial Effects of Fungi
INTERNET LINKS TO USEFUL WEB SITES
FILM ON FUNGI SHOWN IN CLASS