BIOL 1407
Review Sheet Ch. 31 Fungi Mr. Sanregret
1) Kingdom Fungi is within Domain Eukarya. Fungi are chemoheterotrophic. Like animals, they must
acquire food from outside themselves for organic carbon and energy. Unlike animals, fungi do not
ingest food, they secrete digestive enzymes onto their food outside their bodies which break the food
into monomers, then absorb the nutrient molecules.
2) Fungi are composed of hyphae (singular, hypha), thin, filaments. Some hyphae lack septa, and are
basically long thin, cells with many nuclei. Other hyphae have septae (singular, septa), walls that
separate each nuclei from the next. Thus, septate hyphae are long chains made of single nucleus cells.
Fungal cells have a cell wall made of chitin (the same sugar polymer of which insect exoskeletons are
composed).
3) Different hyphae may come together and fuse their cytoplasm together in a process called
plasmogamy.
4) Hyphae branch and form the mycelium, the body of the fungus. E.g. when you see a mushroom
growing from a log, it is a mass of tightly packed hyphae.
5) Fungi have no ability to move, but can grow very quickly. Hyphae grow in length but not in width
(unlike plant shoots and roots). This allows fungi to quickly spread over a wide area. The bulk of a
fungal body is often underground or within the substrate that it is consuming, with only the
reproductive structures (e.g. mushrooms) visible. Scientists have identified a single fungus in Oregon
that is spread across ~2,200 acres of land.
6) Fungi usually grow on plants or on dead plant matter. Hyphae are just the right size and shape to
penetrate plant cell walls, allowing them to grow in between plant cells. Some fungi are decomposers
living on dead plant matter. Others parasitize living plants (e.g. rust on wheat). Other fungi live in
mutualistic relationships with plants.
7) The fungal life cycle has three phases: a diploid phase, a haploid phase, and a dikaryotic or
heterokaryotic phase. Heterokaryotic hyphae have different nuclei for different hyphae that have
fused through plasmogamy. Dikaryotic cells have two genetically distinct haploid nuclei.
8) Because fungi have meiosis and fertilization, they are sexually reproducing organisms. Since there is
no egg or sperm, there is no distinction of female or male. Fungi do have two “mating types,”
designated positive and negative. Positive hyphae can only mate with negative hyphae.
9) There are four phyla of fungi:
10) Chytids are flagellated, small, and primitive (this means they most resemble the earliest fungi).
11) Zygomycota live in soil or on decaying material, produce zygospores (each is a zygote protected
within a spore) that can survive harsh conditions. Includes black bread mold. Mycelium is haploid.
12) Sac fungi: Have cup-like fruiting bodies with spores produced on upper surface. Includes morels and
truffles. Myscelium is haploid.
13) Club fungi: Have a club-like fruiting body with spores produced from the gills of the lower surface.
Includes mushrooms and shelf fungi. Have a haploid mycelium during one phase of life cycle, and a
dikaryotic mycelium during another phase (which bears fruiting bodies (e.g. mushrooms).
14) Yeasts, molds, lichens, and mycorrhizae are adaptations found in mulitple fungal phyla.
15) Fungi are usually multicellular. Fungi that are unicellular are called yeasts. Unicellularity in yeasts is
a derived trait, not a primitive trait.
16) A mold is a fungus of any phylum that grows rapidly through asexual reproduction.
17) Lichens are fungi and algae living together in a mutualistic symbiosis (benefits both organisms, and
they live together). The fungus facilitates gas exchange and collection of water and minerals and
protects the algae, while the algae provides food through photosynthesis. Lichens are capable of
surviving in very barren, infertile habitats. For this reason, they are usually among the first organisms
to colonize newly cleared rock or soil (e.g. after a volcanic eruption).
18) Mycorrhizae are fungi that attach to plants and help plants by collecting inorganic nutrients like
nitrogen and phosphorus. In turn, the plants provide sugars from photosynthesis. Mycorrhizae thus act
like plant roots. This way of life has developed independently in different species and phyla of fungi.