Division Fungi

Characteristic of Fungi

• Nutritional modes
• Fungi are heterotrophs which are saprobes (consume dead material) or parasites
• Fungi obtain nourishment by secreting digestive enzymes and then absorbing the broken-down substances
• Fungi are basically an animal turned "inside out"
• Body plans
• Fungi are multicellular organisms composed of filamentous hyphae

• A mass of hyphae is called a mycelium (a mushroom is a mycelium)
• Fungi also possess sporangia during their reproductive cycle

• Hyphae can be haploid (n), diploid (2n), or dikaryoid (n+n)

• Reproductive cycle
• Asexual - sporangia produce haploid spores
• Sexual - gametangia produce gametes
• The asexual mode of reproduction is far more common
• Most major taxonomic groups are differentiated by reproductive cycle

Fungal Taxonomy

Zygomycota Common representatives: black bread molds Hyphae are haploid Reproduction relies mainly on asexual spore production Sexual reproduction: gametangia form a zygospore is then formed where the gametes fuse a sporangia forms, meiosis occurs, and haploid spores are released

Ascomycota (sac fungi) Common representatives: yeasts, morels, and truffles Hyphae are haploid and dikaryoid Asexual reproduction relies on asexual spore production Sexual reproduction: multicellular spore-producing structure (ascocarp) forms nuclei in dikaryoid hyphae fuse meiosis occurs and haploid spores are released

Basidiomycota (sac fungi) Common representatives: mushrooms and shelf fungi Hyphae are haploid and dikaryoid Asexual reproduction relies on asexual spore production this is much rarer in basidiomycetes than in zygomycetes or ascomycetes Sexual reproduction: multicellular spore-producing structures (basidiocarps) form nuclei in dikaryoid hyphae fuse meiosis occurs and haploid spores are released

Deuteromycota (fungi imperfecti)

• The major divisions of fungi are based on sexual reproduction mode. What happens if the sexual stage of a fungi is not known?
• All of these fungi are lumped into a fourth group for simplicity
• Members include Trichophyton (Athlete's foot), Penicillium (Penicillin), and Candida albicans ("Yeast" infections).

Symbiosis between Fungi and Plants

Lichens Lichens are the product of a symbiosis between a fungi and an algae The fungi envelops the algae and derive nutrition from the algae The fungi provides water and shelter for the algae Lichens can absorb minerals from rock and nitrogen from the air

Mycorrhizal fungi Mycorrhizae are fungi with a symbiotic relationship with land plants The fungi regulates ion flow into the plants and in turn is supplied with carbohydrates Some of the earliest terrestrial plant fossils show evidence of mycorrhizal associations This implies that this symbiosis was important, if not crucial, for the colonization of the land by plants