Key Points on Free-Living Protozoa

Oct 16, 2024

Lecture on Protists

Introduction to Protists

  • Protists are eukaryotes that do not fit into the categories of plants, fungi, or animals.
  • Historically classified under Kingdom Protista, but due to diversity, this is no longer considered a kingdom.
  • Classification:
    • Protozoa: Animal-like protists
    • Algae: Plant-like protists
    • Slime molds and water molds: Fungal-like protists

Characteristics of Protozoa

  • Chemoheterotrophs similar to animals; many are motile.
  • Lack cell walls.
  • Ingest nutrients similarly to animals.

Study Focus

  • Free-living protozoa examples: Euglena, Paramecium, and Amoeba Proteus.

Amoeba Proteus

  • Found in micro B box slides 23 and 24.
  • Characteristics:
    • Unicellular, lack a cell wall.
    • Use pseudopods for movement and phagocytosis (food acquisition).
    • Environment: Freshwater, oxygen-rich, prefer low light conditions (e.g. under lily pads).
    • Can form cysts under harsh conditions.
  • Structures to Identify:
    • Nucleus (contains DNA)
    • Pseudopods
    • Contractile vacuoles (pump excess water to avoid osmotic lysis)

Euglena

  • Found in micro B box slides 25 and 26.
  • Characteristics:
    • Mixotrophs: Can photosynthesize in light (photoautotroph) and ingest food in darkness (chemoheterotroph).
    • Possess chloroplasts from secondary endosymbiosis with algae.
    • Motile with flagella; have a pellicle (protein plates) allowing amoeboid movement.
    • Exhibit phototaxis using a stigma or eyespot.
  • Structures to Identify:
    • Flagella
    • Chloroplasts
    • Nucleus
    • Stigma (eyespot)
    • Contractile vacuoles

Paramecium

  • Characteristics:
    • Ciliated protozoan, covered with cilia for motility and food acquisition.
    • Cilia guide food into gullet for phagocytosis.
    • Chemoheterotrophs; some may have symbiotic algae.
    • Have two nuclei: macronucleus (general functions) and micronucleus (sexual reproduction).
  • Processes:
    • Endocytosis: Engulfing food into vacuoles.
    • Exocytosis: Expelling waste from vacuoles at a specific cell membrane site.
  • Structures to Identify:
    • Macro and micronuclei
    • Contractile vacuoles

Conclusion

  • Further videos will cover symbiotic protozoa, including pathogenic examples like Giardia and Plasmodium.

These lecture notes summarize key points about free-living protozoa for lab study, focusing on Amoeba Proteus, Euglena, and Paramecium. They include essential characteristics, functions, and structures to identify for each organism.