Biology II

Fungi

Introduction of Fungi

• They are classified as eukaryotes (have a membrane bound nucleus)

• Fungi can be divided into two basic morphological forms:– Yeasts– Hyphae

Yeast

• Unicellular fungi• Reproduce asexually by blastoconidia

formation (budding) or fission

Hyphae

• Multicellular• Reproduce asexually and/or sexually

• Most Fungi occur in the hyphae form as branching, threadlike tubular filaments– Lack cross walls (coenocytic)– Have cross walls (septate)– Clamp connections at the septa which connect the

hyphae elements

Common Characteristics of Fungi

• Heterotrophy-eat other organisms as food– Three major categories of heterotrophs• Saprophytes-Feed on dead tissue or organic waste• Symbionts- mutually beneficial relationship between a

fungus and another organism• Parasites- feeding on living tissue of a host

– Parasites that cause diseases are called pathogens– Some parasites are obligate parasites (require a living host)– Others are facultative or nonobligate (do not require a living

host in order to survive)

Common Characteristics

• Body Form– Unicellular– Filamentous-tube-like strands called hypha or

hyphae– Mycelium- total of hyphae– Sclerotium=Hardened mass of mycelium that

generally serves as an overwintering stage– Multicellular-such as mycelial cords, rhizomorphs,

and fruit bodies (mushrooms)

Common Characteristics

• Fungus is often hidden from view– It grows through its food source, excretes

extracellular digestive enzymes, and absorbs dissolved food

• Indeterminate growth

Common Characteristics

• Spores- asexual (product of mitosis) or sexual (product of meiosis) in origin– Purpose of Spores• Allows the fungus to move to new food source• Resistant stage- allows fungus to survive periods od

adversity• Means of introducing new genetic combinations into a

population

Common Characteristics

• Vegetative phase of fungus is generally sedentary

• Cell wall present, composed of cellulose and/or chitin

• Food Storage- generally in the form of lipids and glycogen

• Eukaryotes-true nucleus and other organelles present

Common Characteristics

• All fungi require water and oxygen• Fungi grow in almost every habitat

imaginable, as long as there is some type of organic mater present and the environment is not too extreme

• Diverse group, number of describer species is about 69,000 (estimated 1.5 million species total)

Phylums of Fungi

• Phylum Zygomycota- common mold found on land– Reproduce by zygospores– Ex: Rhizopus- common bread mold– Contain root-like structures (rhizoids) to anchor in

bread. Stolons on surface of bread.

Phylum Basidiomycota

• Basidiomycetes- the club fungi, about 22,300 species

• Includes mushrooms, toadstools, puffballs, shelf fungi, rusts, bird’s nest fungi and smuts

• Characterized by perforate septate hypahe and the production of basidium (club) following sexual reproduction.