Protozoa are best described as which of the following?

• A. Single-celled microscopic plants
• B. Single-celled microscopic animals without a rigid cell wall
• C. Multicellular organisms
• D. Prions

Answer: (B)

Protozoa are single-celled, microscopic eukaryotes that act like animals in how they feed and move. They are heterotrophs, typically taking in food rather than making it themselves, and they move using flagella, cilia, or pseudopods. A key feature is that they lack a rigid cell wall, giving them flexible membranes to help with movement and shape. Because of these animal-like, unicellular characteristics, they’re best described as single-celled microscopic animals without a rigid cell wall. They’re not plants (which usually photosynthesize and have rigid cell walls made of cellulose), not multicellular organisms, and not prions (which are misfolded proteins, not cells).