Yes, protozoa are always unicellular. According to biological classifications, these fascinating microorganisms consist of a single cell.
Protozoa are a diverse group of eukaryotic microorganisms. Unlike plants or algae, they are nonphotosynthetic, meaning they do not produce their own food through photosynthesis. Instead, they obtain nutrients by ingesting other organisms or organic matter. A defining characteristic of protozoa, as highlighted by scientific understanding, is their motility—they are capable of movement, often using structures like flagella, cilia, or pseudopods.
Key Characteristics of Protozoa
To better understand protozoa, consider the following definitive traits:
- Unicellular Nature: Each protozoan is a complete organism composed of a single cell. This distinguishes them from multicellular organisms like animals or plants.
- Nonphotosynthetic: They are heterotrophs, relying on external sources for nutrition. This means they do not contain chloroplasts for photosynthesis.
- Motility: Protozoa are typically capable of independent movement, which aids in their search for food and escape from predators.
- Eukaryotic: Like all protists, protozoa are eukaryotes, meaning their cells possess a true nucleus enclosed within a nuclear membrane, as well as other membrane-bound organelles.
The reference specifically states: "Protozoa, on the other hand, are nonphotosynthetic, motile organisms that are always unicellular." This clearly confirms their singular cellular nature. While the broader group of protists, to which protozoa belong, can include both unicellular and some simple multicellular forms, protozoa themselves are strictly defined by their unicellularity.
