Key Concepts in Fungal Diversity and Ecology

Fungal Diversity

  • Characteristics of Fungi:
    • Chitin in Cell Walls: Fungi have chitin, unlike plants which have cellulose.
    • Heterotrophs:
    • Obtain organic matter from other organisms (like animals and choanoflagellates).
    • Absorptive Nutrition:
    • Saprobes: absorb nutrients from dead organic matter.
    • Secrete digestive enzymes externally to absorb nutrients (live in their food).
    • Other Nutritional Strategies:
    • Mutualists: exchange nutrients with partners.
    • Parasites: extract nutrients from living hosts without their consent.

Morphology of Fungi

  • Single-Celled vs. Multicellular Forms:
    • Unicellular: E.g., yeast.
    • Multicellular:
    • Hyphae: root-like structures.
    • Mycelium: network of hyphae, responsible for nutrient absorption and the formation of fruiting bodies.
  • Surface Area to Volume Ratio:
    • High ratio in mycelium allows efficient absorption of water and nutrients.
  • Fruiting Bodies:
    • Produce spores; developed from mycelium.

Reproduction in Fungi

  • Haploid Dominance:
    • Most of the fungal life cycle involves a single set of chromosomes.
  • Reproductive Strategies:
    • Asexual Reproduction:
    • Haploid spores produce haploid hyphae which give rise to more spores.
    • Sexual Reproduction:
    • Fusion of haploid hyphae of different mating types (morphologically identical).
  • Dikaryotic Phase:
    • Fusion of two haploid hyphae results in dikaryotic hyphae (two genetically different nuclei).
    • Stages of Sexual Reproduction:
    • Plasmogamy: fusion of cytoplasm.
    • Karyogamy: fusion of nuclei.

Spore Location and Dispersal

  • Spores often produced on gill surfaces in gilled mushrooms.
  • Dispersal Mechanisms:
    • Physical: Wind, water, and animals (e.g., birds).
    • Herbivore Digestion: Spores survive passage through the digestive systems of herbivores.

Mutualistic Relationships

  • Fungi and Plants: Mycorrhizae (fungi absorb water/minerals; plants provide sugars).
  • Fungi and Algae/Cyanobacteria: Lichen (fungus provides protection; algae/cyanobacteria provide carbon compounds).
  • Fungi and Animals: E.g., leafcutter ants (mutual feeding relationship).

Parasitic Fungi

  • Examples:
    • Cordyceps infects insects.
    • Coccidioides causes valley fever in humans.

Competitive Interactions

  • Intraspecific Competition: Within species (e.g., mates, space).
  • Interspecific Competition: Between different species (e.g., space, resources).
  • Niche:
    • Fundamental Niche: Potential range of conditions a species could occupy.
    • Realized Niche: Actual conditions a species occupies due to competition.

Succession and Community Changes

  • Primary Succession: Colonization of bare land (slow process).
  • Pioneer Species: First to colonize; hardy, short-lived, and often wind-pollinated species.
  • Late-Successional Species: Larger, longer-lived species; tolerant of shade; not replaced by incoming species.
  • Disturbances: Drive community dynamics and affect species diversity.

Measuring Community Structure

  • Species Richness: Count of different species present.
  • Species Evenness: Distribution of individuals among species.
  • Species Diversity: Combines richness and evenness (measured by the Shannon-Weiner index).

Energy in Ecosystems

  • Energy Flow:
    • Energy enters from sunlight; producers (plants) convert light energy to chemical energy.
    • Trophic Levels:
    • Producers → Primary Consumers → Secondary Consumers → Tertiary Consumers.
    • Only about 10% of energy is transferred between trophic levels.
  • Net Primary Productivity (NPP): Amount of energy available for consumers after respiration.

Carbon Dating

  • Carbon Isotopes: C12 (stable), C14 (unstable, decays over time).
  • Ratio of C14 to C12 helps determine the age of carbon-based life forms based on its half-life.

Paleoecology

  • Study of past ecological communities through proxies (physical, chemical, or biological materials preserved in geological records).
  • Use proxies to reconstruct past environments and infer ecological conditions.