BIO_114 LAB 3

LAB 3 - KINGDOM FUNGI

Fungal Characteristics

• Cell Composition:

  • Cell walls are made of chitin.

• Nutritional Mode:

  • Heterotrophs and major decomposers.

• Body Structure:

  • Composed of long filaments known as hyphae, which collectively form a structure called mycelium.

• Reproductive Methods:

  • Asexual reproduction through the production of spores.

  • Sexual reproduction involves the mating of hyphae filaments.

Types of Hyphae

• Coenocytic Hyphae:

  • Characterized by the nucleus of each cell embedded in the cytoplasm without cross walls.

  • Examples: Zygomycota, Oomycota (now classified among the Protista).

• Septate Hyphae:

  • Contain cross walls.

  • Examples: Basidiomycota, Ascomycota.

Fungal Phyla Overview

• Five Main Phyla of Fungi:

  • Focus within the lab on:

    • Phylum Zygomycota (zygomycetes - bread molds):

      • Meiospores produced by zygosporangium (a resistant microscopic structure).

    • Phylum Ascomycota (ascomycetes - sac fungi):

      • Meiospores produced in sac-like structures called asci, contained in fruiting bodies (ascoma).

    • Phylum Basidiomycota (basidiomycetes - club fungi):

      • Meiospores produced on club-shaped basidia contained in fruiting bodies (basidioma).

Additional Fungal Phyla

• Phylum Chytridiomycota:

  • Most primitive fungi, aquatic, disperses via swimming zoospores.

  • Reproduces both sexually and asexually.

  • Notable for causing white-nose syndrome in bats and loss of amphibian diversity.

• Phylum Glomeromycota:

  • Critical symbionts to terrestrial plants determining arbuscular mycorrhizae.

  • Form mutually beneficial associations with plant roots, providing minerals in exchange for carbohydrates.

  • Does not reproduce sexually or survive without plant roots; characterized by coenocytic hyphae but does not form zygospores.

• Group Deuteromycetes (Imperfect Fungi):

  • No known sexual reproduction, reproduces only asexually through mitospores.

  • Transitional group and not considered a valid phylogenetic group.

Exercise A: Phylum Zygomycota

• Characteristics:

  • Small group (approximately 1,000 species).

  • Forms coenocytic hyphae without crosswalls.

• Key Traits:

  • Zygosporangium is a thick-walled, stress-resistant structure.

  • Lacks dikaryotic hyphae; karyogamy occurs followed by meiosis.

  • Zygospore can remain dormant for extended periods; germination occurs via meiosis.

Zygomycota Overview

• Role:

  • Primarily decomposers.

  • Asexual spores produced in sporangia; sexual reproduction involves formation of zygospores.

• Common Mold Example:

  • Rhizopus, which penetrates bread and forms fruiting bodies. Mycelium consists of a mass of hyphae or filaments.

Exercise B: Phylum Ascomycota

• Characteristics:

  • Largest group of fungi, comprising roughly 32,000 species.

  • Examples include Scarlet cup, Carbon fungus, Morel.

• Key Traits:

  • Possesses septate hyphae with cellular cross-walls.

  • Meiospores (ascospores) formed within asci in ascoma (fruiting body).

  • Mitospores (conidia) produced by pinching off of hyphal tips.

Yeasts in Ascomycota

• Role:

  • Significant group used in fermentation, contributing billions to industries such as winemaking and baking.

  • Can also cause diseases, including yeast infections.

• Valuable Species:

  • Some ascomata are highly prized culinary delicacies like truffles and morels.

Exercise C: Phylum Basidiomycota

• Characteristics:

  • Comprised of a large group with approximately 22,000 species.

  • Presence of septate hyphae with cross-walls.

• Key Traits:

  • Meiospores formed on club-shaped basidia in basidioma (fruiting structure).

  • Organism life predominantly consists of dikaryotic hyphae.

  • Meiospores are generated from mating of different hyphal types.

Basidiomycota in Nature

• Notable Forms:

  • Includes diverse structures such as mushrooms, stinkhorns, and jelly fungi.

  • Can form fairy rings, with many species decomposing organic debris in soil.

• Ecological Importance:

  • Significant decomposers and play roles as food sources (including edible forms) and as pathogens of plant crops.

  • Examples include Amanita (death cap fungus), corn smut, and ergot affecting wheat.

Fungal Groups: Deuteromycetes

• Description:

  • Comprises approximately 17,000 species with septate hyphae,

  • Exclusively reproduces asexually via conidia.

• Significance:

  • Play roles in decomposition, food production (e.g., cheeses), and source of antibiotics (e.g., penicillin).

Special Fungal Mutualisms: Lichens

• Definition:

  • Symbiotic relationship between fungi and unicellular photosynthesizers (green algae or cyanobacteria).

• Mutual Benefits:

  • Fungi provide shelter and minerals; photosynthetic partners provide sugars to fungi.

• Ecological Role:

  • Vital for primary succession and able to colonize harsh environments.

  • Lichens can serve as bioindicators of air quality.

Lichens Growth Forms

• Growth Forms:

  • Crustose

  • Foliose

  • Fruticose

Mycorrhizal Associations

• Definition:

  • Associations between fungi and plant roots, with around 90% of plants participating.

• Mutualism Details:

  • Fungi improve nutrient and water uptake for plants; plants supply sugars to fungi.

• Types:

  • Arbuscular mycorrhizae (endomycorrhizae) penetrates root cells.

  • Ectomycorrhizae surrounds root cells.