Kingdom Protista and Protozoans

  • Objectives of Section 19.1

    • Identify characteristics of Kingdom Protista.
    • Compare and contrast the four main groups of protozoans.

  • Vocabulary

    • Eukaryote: An organism whose cells contain membrane-bound organelles, can be unicellular or multicellular.
    • Protozoan: Unicellular, animal-like protists.
    • Alga: Plant-like protist, can be unicellular or multicellular, uses photosynthesis.
    • Pseudopodia: Extensions of cytoplasm in certain protozoans for movement and feeding.
    • Asexual reproduction: Mode of reproduction involving only one parent.
    • Flagellate: Protozoan that uses flagella for movement.
    • Ciliate: Protozoan that uses cilia for movement.
    • Sporozoan: Protozoan that produces spores, often parasitic.
    • Spore: Reproductive cell that forms without fertilization, leading to a new organism.

  • Characteristics of Kingdom Protista

    • Includes a vast diversity of organisms: unicellular/multicellular, microscopic/large, heterotrophic/autotrophic.
    • All protists are eukaryotes, differing from bacteria.
    • Grouped into three main categories:
    • Animal-like Protists (Protozoa): Unicellular heterotrophs that feed on other organisms.
    • Plant-like Protists (Algae): Autotrophic, perform photosynthesis, lack complex organs.
    • Fungus-like Protists: Decompose organic material, can move at some life stage, do not have chitin in cell walls.

  • Diversity of Protozoans

    • All protozoans are unicellular heterotrophs.
    • Reproduction typically asexual, some also sexual.
    • Four primary groups based on movement:
    • Amoebas: Use pseudopodia, shapeless, live in moist environments.
    • Flagellates: Move using flagella, some are parasites (e.g., cause diseases).
    • Ciliates: Use cilia for movement, complex structures (e.g., paramecium).
    • Sporozoans: Internal parasites, reproduce spores, complex life cycles (e.g., Plasmodium which causes malaria).

  • Amoebas

    • Part of phylum Rhizopoda, no cell wall, utilize pseudopodia to move and feed.
    • Found in saltwater and freshwater; contractile vacuoles manage excess intake of water.
    • Examples: Foraminiferans (calcium carbonate shells) and radiolarians (silica shells).

  • Flagellates

    • Part of phylum Zoomastigina; characterized by flagella which they whip for movement.
    • Some are mutualistic (e.g., help termites digest wood), while others are harmful parasites.

  • Ciliates

    • Part of phylum Ciliophora; covered by cilia for movement.
    • Paramecium as a representative:
    • Has an oral groove for feeding, contractile vacuoles for water regulation.
    • Reproduces through asexual division and can undergo conjugation.

  • Sporozoans

    • All are parasitic—live inside host organisms (e.g., Plasmodium spp. that cause malaria).
    • Complex life cycles involving multiple hosts (mosquitoes and humans in malaria).

  • The Life Cycle of Plasmodium

    • Stages: Gametes, zygote, sporozoites, and their development in hosts.
    • Symptoms: Malaria causes severe health issues worldwide; complicated by drug resistance.

  • Conclusion: Protista represents an incredibly diverse kingdom with varying nutritional methods (heterotrophic, autotrophic) and movement mechanisms (pseudopodia, flagella, cilia). The relationships between these organisms and their impact on ecosystems are profound, with significant implications on health.