Lab 7 – The Kingdom Fungi

Lab Objectives

  • Describe characteristics of the kingdom Fungi.
  • Understand sexual and asexual reproduction in major groups of Fungi.
  • Know life cycles of significant fungal groups.

Introduction to Fungi

  • Fungi are distinct eukaryotic organisms, categorized in their own kingdom.
  • Nutrition:
    • Saprophytes: Obtain food from dead organic matter.
    • Parasites: Feed on living organisms.
    • Fungi are key decomposers in ecosystems.
  • Structure:
    • Hypha: Filamentous strands of cells.
    • Can be septate (with crosswalls) or coenocytic (without crosswalls).
    • Mycelium: Mass of hyphae forming the organism.
    • Fungal cell walls contain chitin instead of cellulose.
    • Haustoria: Specialized hyphae for nutrient absorption from living cells.

Reproduction in Fungi

  • Asexual Reproduction:

    • By spores: Microscopic and spread via air/water (e.g., mold).
    • Budding: Uneven mitosis, common in yeasts.
    • Fragmentation: Breaking of hyphae into pieces that develop into new individuals.

  • Sexual Reproduction Steps:

    1. Chemical Attraction: Hyphae release pheromones to attract compatible partners.
    2. Plasmogamy: Fusion of cytoplasm from compatible hyphae.
    3. Karyogamy: Fusion of haploid nuclei, forming diploid cells.
    4. Meiosis: Restores haploid condition, leading to spore formation.

Fungal Classification

  • Five major phyla based on reproductive structures:
    1. Chytridiomycota: Motile spores with flagella.
    2. Zoopagomycota: Resistant zygosporangium.
    3. Glomeromycota: Asexually forming spores, key in mycorrhizal symbiosis with plants.
    4. Ascomycota: Sac fungi, produce spores internally in asci.
    5. Basidiomycota: Club fungi, spores formed externally on basidia.

Highlights of Phyla

  • Chytridiomycota: Ancient fungi, aquatic, absorb nutrients, flagellated spores.
  • Zoopagomycota: Bread molds, saprophytic, lack septa.
  • Glomeromycota: Essential for soil health, facilitates plant nutrient uptake through mycorrhizal relationships.
  • Ascomycota: Large group, includes molds and yeasts; forms conidia (asexual spores).
  • Basidiomycota: Familiar mushrooms, important for food supply/poisonous risks.

Lichens

  • Symbiotic associations between fungi (usually ascomycetes) and photosynthetic organisms (algae/cyanobacteria).
  • Reproduction by fragmentation or stress-resistant packets.
  • Growth forms:
    • Crustose: Flat, adheres closely to substrate.
    • Foliose: Leaf-like, some peeling from substrate.
    • Fruticose: Erect stalks, three-dimensional.
  • Sensitive to pollution due to nutrient absorption capabilities.