fungi

• Mycology


  The scientific study of fungi
• Characteristics of fungi

  • Heterotrophic - 'Feed' through absorption; secrete enzymes outside their body to break down organic molecules
  • Asexual and sexual production of spores
  • Diverse ecological niches - Decomposers, Mutualists, Parasites
  • Two types of body structures - Single cells (yeasts), Multicellular filaments

  
• Fungi have cell walls made of chitin
• Multicellular fungi have branching filaments called hyphae comprising the mycelium

  
• This filamentous morphology aids in nutrient absorption
• Mycorrhizae

  Symbiosis between fungi and plant roots

  
• Fungi reproduce through sexual or asexual reproduction

  • Most of the time, fungi are in a haploid state
  • Fungi have a heterokaryotic stage, where the cell has two haploid nuclei which remain separate

  
• Sexual reproduction in fungi

  1. Haploid fungal hyphae consist of different 'mating types'

  2. Fungi use pheromones to signal mating type

  3. When different mating types interact, the cytoplasm joins in plasmogamy

  4. Haploid nuclei do not immediately fuse and coexist in a heterokaryon

  5. During karyogamy, the haploid nuclei fuse, producing a diploid zygote

  6. The zygote undergoes meiosis, producing haploid spores

  
• Fungi reproduce through sexual or asexual reproduction

  
• Reproduction types

  • genetically identical offspring
  • genetically non-identical offspring
• Some fungi only reproduce asexually
• Deuteromycetes

  Have no known sexual stage
• Deuteromycetes produce spores through mitosis or whole organisms through budding

  
• Phylogenetic position of deuteromycetes is currently debated
• Phylogeny of Fungi

  • Fungal phylogeny has undergone extensive recent change
  • Estimates point to there existing 2-4 million species of fungi on earth

  
• Fungal phyla

  • Cryptomycetes and microsporidians (1,300 species) - basal fungi, parasitic
  • Chytrids (1,000 species) - flagellated spores (zoospores), several species have contributed to the decline of worldwide amphibian populations
  • Zoopagomycetes (900 species) - most parasitize animal species
  • Mucoromycetes (750 species) - includes many molds on plants and foods
  • Ascomycetes (90,000 species) - "sac" fungi, sexual reproduction involves an ascocarp and asci
  • Basidiomycetes (50,000 species) - "club" fungi (mushrooms), sexual reproduction involves a basidiocarp and basidia

  
• Ascomycetes

  • ascocarp, asci