Amoeba: A Protozoan Cheat Sheet

Amoeba are single-celled eukaryotic organisms belonging to Phylum Protozoa, characterized by their irregular shape, movement via pseudopodia, and diverse modes of nutrition and reproduction.

Core Principles

Protozoans are microscopic, unicellular animals.
They can be free-living, parasitic, commensal, or symbiotic.
The body is naked or covered by a pellicle; some have shells or tests.
Protoplasm is differentiated into ectoplasm and endoplasm.
Locomotion is achieved through pseudopodia, cilia, or flagella.
Nutrition varies: holozoic, holophytic, saprophytic, or parasitic.
Respiration and excretion occur via diffusion through the body surface or contractile vacuole.
Reproduction is asexual (binary fission, multiple fission) and/or sexual.
Encystment is a survival mechanism during unfavorable conditions.

Key Terms

Pseudopodia: Temporary, arm-like extensions of the cytoplasm used for locomotion and engulfing food.
Ectoplasm: The outer, more viscous layer of the protoplasm.
Endoplasm: The inner, more fluid layer of the protoplasm, containing organelles.
Contractile Vacuole: An organelle that regulates water content and expels excess water.
Food Vacuole: A vesicle within the cytoplasm where digestion of ingested food occurs.
Binary Fission: Asexual reproduction where one cell divides into two identical daughter cells.
Multiple Fission: Asexual reproduction where one nucleus divides multiple times, followed by cytoplasmic division, forming many daughter cells.
Encystment: A dormant stage where the protozoan forms a protective cyst wall to survive harsh conditions.