Fungi

• Why Fungi are Important

  • Decomposers - break down dead and decaying plant and animal matter so the nutrients can be reused by plants
  • Food production - yeast is used to make bread, wine, and beer
  • Medicinal uses - Penicillium produces an antibiotic
  • Food source - we eat mushrooms and truffles
  • Succession - lichens (combination of an algae and a fungus) grow on bare rock and help form the first soil layer
• Why Fungi are Harmful


  • Cause disease to animals (athlete's foot and ringworm) and plants
  • Responsible for destroying 10-50% of the world's fruit harvest per year
• Fungi are not Plants
• Chitin


  A complex chemical found in the cell walls of fungi and in the external coverings of insects and crustaceans such as lobsters and crabs
• 5 Major Phyla of Fungi

  • Zygomycetes: bread moulds, eg. Rhizopus
  • Ascomycetes: yeast
  • Basidiomycetes: mushrooms
  • Chytridiomycota: only fungi with swimming spores
  • Glomeromycota: form symbiotic relationships with plant roots

  
• Over 100 000 different species of fungi
• Fungal bodies


  • Mesh-like composed of branching network of filaments called mycelium
  • Filaments are known as hyphae. They are microscopically thin consisting of tubes of cytoplasm containing nuclei
  • Cytoplasm is contained by a cell wall made of chitin
  • Materials move relatively quickly through the hyphae
  • Hyphae form fuzz often associated with mould and they form reproductive structures of fungi
  • Some fungi are single-celled (e.g. yeast)
• Extracellular digestion in fungi

  • Nutrients digested externally, then absorbed
  • Absorption done by a mesh of branching filaments called mycelia
  • Mycelia grow on or below the surface on which it grows (substrate)
  • Each filament is called a hyphae - "the fuzz"
• Life Cycle of a Mushroom

  1. Haploid parent hyphae fuse and become dikaryotic (cell contains 2 haploid nuclei)

  2. New hypha enlarges and breaks through soil as a button

  3. Button matures to form a stalk and cap

  4. Gills (made of hyphae) inside cap mature and grow extensions

  5. Two haploid nuclei in extension fuse to form a diploid cell

  6. Cell undergoes meiosis to produce 4 haploid spores

  7. Cap opens and gills release spores which are carried by wind

  8. Spores germinate (sprout) if it lands in a favourable environment