The Mycota or Fungi are non-photosynthetic eucaryotes adapted
to absorptive nutrition. Slime molds have motile, unicellular, vegetative
stages, while true fungi form branched filaments (hyphae) that invade dead
or decaying material. All fungi form spores; the various groups of fungi
are distinguished by their means of spore formation.
General characteristics of fungi: Plastids and chlorophyll are absent.
Cell walls are made of chitin, not cellulose. Cell membranes sometimes break
down to form binucleated cells or multinucleated aggregates. Reproductive
structures vary, but spores are always produced. Nutrition is usually
absorptive; many fungi live on dead or decaying matter (saprophytic),
but some are parasitic instead. Fungi are important as decay organisms in
freshwater and terrestrial ecosystems. Most prefer moist conditions for
optimal growth.
Slime molds: Organisms whose unicellular vegetative stages are either
amoeboid or flagellated and resemble Amoebozoans. All types have a multinucleated
or multicellular creeping stage that forms spore-producing bodies. Each spore
develops into a new vegetative cell.
Formerly considered to be fungi, but now
usually put in their own group.
True fungi (Eumycota): Fungi whose vegetative structure typically
consists of a series of branching filaments (hyphae) forming a
tuft (mycelium).
Fungi (view here)
- Chytrids: Primitive, aquatic fungi that
reproduce by flagellated cells (zoospores).
Includes Phytophthora, responsible for the 1841 devastation of the Irish potato crop.
- Glomerulomycota: Fungi that are often attracted to plant roots, where they
form symbiotic associations (mycorrhizae) that benefit both species.
- Zygomycota (black bread molds, etc.): Reproduce by conjugation of
hyphae that come together and form nonmotile spores.
- Ascomycetes (Ascomycota) (yeasts, cup fungi, truffles, etc.):
spores are produced, 4 or 8 at a time, in sacs (asci).
Included genera of commercial or medical importance:
- Saccharomyces, a yeast
used commercially in the production of both bread and beer.
- Penicillium, responsible for penicillin, also for roquefort and camembert cheeses.
- Candida, responsible for vaginal yeast infections, also for mouth infections ("thrush").
- Several genera of "dermatophyte" fungi, responsible for ringworm and athlete's foot.
- Basidiomycetes (Basidiomycota) (mushrooms, puffballs, rusts, smuts, etc.): spores
are produced, usually 4 at a time, at the tips of club-like organs
(basidia).
Lichens: Very intimate symbiotic associations of fungi with either
algae or cyanobacteria. The fungus absorbs and retains sufficient moisture
for both partners; the green partner photosynthesizes and provides food.
Lichens are often the first colonizers of bare rock surfaces.
REVIEW:
Study guide and vocabulary
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