Kingdom Fungi and Plantae Study Notes

Kingdom Fungi

Key Characteristics

  • Decomposers: Bacteria and fungi serve as the most significant recyclers on Earth by breaking down dead organic material.
  • Heterotrophs: Organisms that obtain nutrients through extracellular digestion.
  • Saprobes vs. Symbionts:
    • Saprobes: Acquire nutrients from dead organic matter.
    • Symbionts: Acquire nutrients from living, organic matter.

Structural Features

  1. Chitin-based Cell Wall

    • Provides structural support and protection.

  2. General Morphology

    • Thallus/Mycelium: The main body of the fungal organism.
    • Hyphae: Filaments that compose the thallus/mycelium.
      • Septate Hyphae: Characterized by cell walls that partition cells.
      • Coenocytic Hyphae: Lack cell wall partitions.
    • Haustoria: Specialized hyphae that release exoenzymes for extracellular digestion.

Reproductive Strategies

  1. Fertilization

    • Syngamy: Initial fusion of cytoplasm from two different cell types.
    • Plasmogamy: Fusion of cytoplasm without nucleus fusion.
    • Karyogamy: Fusion of nuclei, creating genetically unique spores.
    • Dikaryon (Heterokaryon): A cell containing two haploid nuclei from different individuals, often displayed as a transitional ploidy state denoted as "n+n".
    • Eventually, karyogamy leads to meiosis, producing spores.

  2. Spores: Serve for dispersion and survival of fungal species.

Major Fungal Phyla

  1. Phylum Zygomycota

    • Characteristics: Spores dispersed by air, hyphae are typically coenocytic.
    • Example: Rhizopus (Black bread mold).
    • Reproduction: Involves sexual and asexual processes.

  2. Phylum Ascomycota (Largest class)

    • Characteristics: Free-living & symbiotic, spores dispersed by air; septate hyphae with perforated cells.
    • Ascus/Spore Sac: Forms ascocarp, involved in reproduction.
    • Representatives:
      • Peziza
      • Saccharomyces (Yeast)
      • Claviceps (Rye ergot)
      • Penicillium (Source of penicillin, the first antibiotic)
      • Morels and truffles
      • Fermented products like cheese, wine, and bread.

  3. Phylum Basidiomycota

    • Characteristics: Spores dispersed by air, septate hyphae.
    • Basidium/Basidiocarp: Involved in reproduction.
    • Representatives:
      • Mushrooms
      • Toadstools
      • Puffballs
      • Bracket fungi.

  4. Phylum Deuteromycota (Imperfect fungi)

    • Characteristics: No observed sexual reproduction; reproduce asexually via conidiospores.
    • Representatives:
      • Molds
      • Ringworm (not a worm)
      • Predatory fungi capturing nematode worms using modified hyphae.

Significant Fungal Symbioses

  1. Mycorrhizae: Mutualistic association between plant roots and fungi, enhancing nutrient uptake.
  2. Lichens: Mutualistic relationships between fungi and algae or cyanobacteria, important for soil development in terrestrial ecosystems, which can occur in inhospitable environments.
    • Morphological Types: Crustose, Fruticose, and Foliose.

Kingdom Plantae

Key Characteristics

  • Photosynthetic Autotrophs: Possessions of cellulose-based cell walls.

Reproductive Cycle

  • Alternation of Generations: Plants exhibit a lifecycle where fertilization involves the fusion of cytoplasm from different gametes (Plasmogamy), and karyogamy almost immediately leads to the formation of a diploid zygote.
    • Dikaryon: Transient in plants as it quickly transitions to a diploid state.
    • Sporic Meiosis: Plants undergo meiotic processes that produce spores, not gametes. Two distinct generations alternate:
    • Sporophyte: Diploid, produces spores.
    • Gametophyte: Haploid, generates gametes.

Types of Spores

  • Homospory: Produces one type of spore that results in a gametophyte capable of producing both eggs and sperm.
  • Heterospory: Produces two types of spores:
    • Megaspores: Develop into female gametophytes (eggs).
    • Microspores: Develop into male gametophytes (sperms).

Evolution and Adaptations

  1. Land Plant Colonization: Estimated to have occurred around 400 million years ago, with green algae as likely ancestors facing challenges like water acquisition, gas exchange, and gravity management.
  2. Land Plant Features:
    • Possession of chlorophyll A & B.
    • Starch as a storage medium.
    • Gametes protected within multicellular structures.
    • Presence of stomata and waxy surfaces for gas exchange and moisture retention.

Plant Classification

  1. Nonvascular Plants

    • Characteristics: Lack vascular tissues, presence of gametophyte dominant phases, typically found in moist environments.
    • Phyla:
      • Phylum Bryophyta (Mosses)
      • Phylum Hepatophyta (Liverworts)
      • Phylum Anthocerophyta (Hornworts)

  2. Seedless Vascular Plants

    • Characteristics: Have vascular tissues (xylem & phloem), sporophyte dominant, composed of leaves (microphylls/megaphylls).
    • Phyla:
      • Phylum Lycophyta (Club Mosses)
      • Phylum Psilophyta (Whisk Ferns)
      • Phylum Sphenophyta (Horsetails)
      • Phylum Pterophyta (Ferns)

  3. Seed Plants

    • Characteristics: Reproductive adaptations with gametophytes protected in moist tissues, pollination strategies evolved to assist sperm delivery, evolution of seeds as dispersal and survival units.
    • Phyla Include:
      • Phylum Gymnosperms (Naked-seed plants)
      • Phylum Angiosperms (Flowering plants):
      • Produce flowers and fruits, often co-evolved with animals for reproductive success.
      • Contains cotyledon categories: Monocots (one cotyledon), Eudicots (two cotyledons).