Practice question

Protists predominantly display unicellular organization where single cell performs all metabolic, locomotor, sensory, and reproductive functions via specialized organelles such as flagella, eyespot, and contractile vacuole. Some lineages exhibit colonial aggregations like Volvox or transient multicellular fruiting bodies in Dictyostelium without true tissue differentiation and division of labor. Sizes range from picoeukaryotes under two microns to giant ciliate Stentor reaching one millimeter. Despite occurrence of multicellular brown algae within stramenopiles, overwhelming protistan diversity remains microscopic unicellular, contrasting with obligate multicellularity, tissue layers, and embryogenesis characteristic of plants, animals, and most fungi.