Paramecium: Single-celled, covered in cilia for movement, has a defined shape, and uses a contractile vacuole for water balance.
Algae: Mostly aquatic, photosynthetic, can be single-celled or multicellular, and contain chlorophyll.
Amoeba: Single-celled, shapeless, moves using pseudopodia (false feet), and engulfs food through phagocytosis.