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The Wonderful World of Fungi

What is a Fungus?

Along with bacteria, these are the most important decomposers in the biosphere.

General Terminology

  • mycelium - the entire body of the fungus
  • hyphae - (singular, hypha) threadlike structures of which the mycelium is composed
  • thallus - another term for the mycelium; "body"
  • spore - haploid propagule produced via meiosis
  • sporangium - structure within which spores are produced (either sexually or asexually, depending on life cycle stage)

    The Fungal Life Cycle

  • a fungus is haploid for most of its life cycle
  • individuals are one of two complementary mating types generally called "+" and "-"
  • diploidy is brief, followed by meiosis that gives rise to spores
  • all fungi have essentially the same life cycle, though the parts look different:

  • all are absorptive heterotrophs
  • they secrete digestive enzymes onto their nutrient source and absorb the product
  • The main structural support in the cell walls is chitin
  • Except for one small group (chytrids), fungi lack cellulose
  • no true tissues; the thallus is composed of coenocytic--and sometimes septate--hyphae

  • the main storage carbohydrate is glycogen (as in animals)

  • Fungi exist in different forms

    Major Fungal Taxa

    The earliest fungal phylogenies were based on mode of sexual reproduction. Molecular data have resulted in significant revisions.


    These fungi retain primitive characters that may provide clues about fungal origins.

    Ascomycota - The Sac Fungi

  • About 75% of all described fungal species are ascomycetes.

    Basidiomycota - The Club Fungi

    These are the most commonly recognized fungi, and the most commonly eaten by us (for good or bad reasons).
    • named for the microscopic structure where zygotes undergo meiosis to become (basidio)spores: basidium("club" in Latin)

    Glomeromycota - Vital to Ecosystems

    Mycorrhizae - "fungus roots"

    This is a symbiotic relationship between a fungus and a plant root. (What does each partner get out of the relationship?)

    Some of the most valuable edible organisms in the world are truffles, various species of mycorrhizal fungi.

    Symbiotic Fungi

    Be sure to review the different types of symbiosis.

    Predatory Fungi

  • Arthrobotrys (a Deuteromycete) nabs nematodes and other small prey

    Prey Fungi

  • We eat many species--but be sure you know what you're doing!

    (cookies, anyone?)

    Parasitic Fungi

  • rainforest ascomycete parasitoids that infect arthropods
  • various dermatophytes and other nasties
  • respiratory pathogen Histoplasma capsulatum
  • Dutch Elm disease threatens native U.S. populations of elm trees
  • some fungi which infect rotting food (such as grain crops) can be carcinogenic (e.g., some species of Aspergillis or highly toxic (ascomycete ergots - a smut disease which infects plants).
  • Fungal toxins are collectively known as mycotoxins, and are economically important.
  • A chytrid fungus, Batrachochytrium dendrobatidis, has been implicated in the recent large-scale extinctions of amphbians, worldwide.

    Mutualistic Fungi

  • Lichens - a symbiotic association between a fungus and a photoautotroph.

    Biologists put the FUN in FUNgi.