What is the difference between a fungus and a protist?

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The other day, I was reviewing microbial groups and got stuck explaining the difference between fungi and protists to a classmate. They might seem alike because they’re both eukaryotic, but this breakdown really helped clarify how distinct they are in terms of structure, nutrition, and evolution. It’s clearer now why they belong in different categories.

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Anttilampinen 2025-06-12T17:47:33+00:00 1 Answer 2 views
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  1. fleming
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    2025-06-12T17:49:04+00:00
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    Definition and Classification

    Fungi:

    • Fungi form a monophyletic kingdom (Kingdom Fungi) of heterotrophic eukaryotes characterized by chitinous cell walls, absorptive nutrition, and typically filamentous growth.
    • Major groups include:
      • Ascomycota
      • Basidiomycota
      • Zygomycota
      • Chytridiomycota

    Protists:

    • “Protist” is not a formal taxonomic group but a term for eukaryotic organisms that are not animals, plants, or fungi.
    • They represent a paraphyletic assemblage including various algae, protozoa, slime molds, and water molds.
    • Modern classification places them across multiple supergroups of eukaryotes.

    Cellular Structure

    Fungi:

    • Have cell walls containing chitin (a polymer of N-acetylglucosamine).
    • May exist as single cells (yeasts) or multicellular filaments (hyphae) that form a mycelium.

    Protists:

    • Cell structures vary widely.
    • Some have cell walls made of cellulose, silica, or calcium carbonate; others have only a plasma membrane or protein-based pellicles.
    • Range from unicellular to colonial or multicellular forms.

    Nutrition and Metabolism

    Fungi:

    • Exclusively heterotrophic, using absorptive nutrition.
    • They secrete enzymes and absorb nutrients.
    • Roles include:
      • Saprotrophs (decomposers)
      • Parasites
      • Mutualistic symbionts

    Protists:

    • Have diverse nutritional strategies:
    • Photosynthetic protists (algae) are autotrophs.
    • Heterotrophic protists feed via phagocytosis, absorption, or parasitism.
    • Mixotrophs can switch between autotrophy and heterotrophy.

    Reproduction and Life Cycles

    Fungi:

    • Reproduce both asexually and sexually.
    • Asexual: budding, hyphal fragmentation, or asexual spores.
    • Sexual: fusion of compatible hyphae, meiosis, sexual spores.
    • Often have life cycles with haploid-diploid alternation.

    Protists:

    • Very diverse reproduction:
    • Asexual: binary fission, multiple fission, or budding.
    • Sexual: simple gamete fusion or complex cycles.
    • Parasitic protists may have multi-host life cycles.

    Motility

    Fungi:

    • Generally non-motile in vegetative form.
    • Some reproductive cells (e.g., chytrid zoospores) have flagella.

    Protists:

    • Often motile using:
      • Flagella (e.g., Euglena, Trypanosoma)
      • Cilia (e.g., Paramecium)
      • Pseudopodia (e.g., Amoeba)
      • Gliding (e.g., diatoms)

    Ecological Roles

    Fungi:

    • Decomposers of lignin and cellulose.
    • Form symbioses:
      • Mycorrhizae with plants
      • Lichens with algae or cyanobacteria
    • Some are pathogens.

    Protists:

    • Photosynthetic protists are aquatic primary producers.
    • Heterotrophs serve as consumers and decomposers.
    • Include symbionts and pathogens.

    Evolutionary History

    Fungi:

    • Form a monophyletic group more closely related to animals than plants.

    Protists:

    • Represent ancient and diverse lineages from various evolutionary points.

    Examples

    Fungi:

    • Saccharomyces cerevisiae (baker’s yeast)
    • Agaricus bisporus (button mushroom)
    • Penicillium (antibiotic source)
    • Candida albicans (pathogen)
    • Aspergillus species

    Protists:

    • Algae: Chlamydomonas, diatoms, dinoflagellates
    • Protozoa: Paramecium, Amoeba, Plasmodium
    • Slime molds: Physarum polycephalum, Dictyostelium discoideum
    • Water molds: Phytophthora infestans

    Medical and Economic Significance

    Fungi:

    • Used in food: bread, beer, cheese.
    • Source of antibiotics.
    • Cause diseases like athlete’s foot and invasive mycoses.

    Protists:

    • Pathogens: Plasmodium, Trypanosoma, Entamoeba.
    • Crucial in food webs.
    • Seaweeds and diatoms have economic uses.

    Fungi are a well-defined kingdom with distinct features like chitin cell walls and filamentous growth, while protists are a loose group of eukaryotes not classed as plants, animals, or fungi. Molecular studies continue to refine our understanding of these important organisms.

    Source:
    Adl, S.M., et al. (2019). Revisions to the Classification, Nomenclature, and Diversity of Eukaryotes. Journal of Eukaryotic Microbiology.
    Deacon, J. Fungal Biology.

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