Fungi

Fungus Nutrition

• Fungi are heterotrophs with absorptive nutrition.
• Food is digested outside their bodies.
  • Powerful digestive enzymes breakdown complex organic molecules to simpler compounds.
  • The simpler compounds are then absorbed.
• Three different life styles:
  • Saprobic: Absorb nutrients from non-living organic material (i.e. dead plants and animals, etc.)
  • Parasitic: Absorb nutrients from the cells of living hosts (examples: athlete's foot, yeast infections, etc.)
  • Mutualistic: Absorb nutrients from a host organism which they help in some way (examples: lichen, mycorrhizae, etc)

Fungi: General Characteristics

• Unicellular: A few species are found as single celled organisms (e.g. yeast).
• Multicellular: Most fungi are found like this.
  • Hyphae: tubular filaments that make up most multicellular fungi
    • Coenocytic Hyphae:
      • Word Derivation-
        • Kinos (coeno): Gk for “common”
        • Kutos (cytic): Gk for “vessel”
        • Coenocytic = “Common vessel”
      • hyphae that are not divided into separate cells; the nuclei can move around freely!
        • This is the most common form.
    • Septate Hyphae:
      • Word Derivation-
        • Septate: Latin for “wall”
      • hyphae which have incomplete cross walls called septa. Ribosomes, mitochondria, and nuclei can still move cell to cell.

Figure 31.3, Purves's Life: The Science of Biology, 7th Edition

• Mycelium: a large collection or network of hyphae. It is the visible “structure” of a fungus like the typical mushroom.
  • Can be underground.
  • Can be above ground forming a familiar structure.
• Have cell walls made of chitin.
  • A polysaccharide (sugar)
  • Also found in the exoskeletons of arthropods

Figure 31.1(a), page 575, Campbell's Biology, 5th Edition

Fungus Symbiosis: Mutalism

• Lichens: a mutualistic relationship between algae and fungi
  • Algae: photosynthesizes and therefore provides energy.
  • Fungus: provides structure and protection.
• Mycorrhizae: Mutualistic relationship between plants and fungi
  • Word Breakdown:
    • Myco: fungus
    • Rhizae: root
    • “Root fungus”
  • Over 95 % of all vascular plants have mycorrhizae.
    • Fungus: Increases absorptive surface of plant roots, which helps the plant acquire certain minerals.
    • Plant: Provides fungus with food.