They're not aliens from another planet, in spite of the name! Protozoa are unicellular (one-celled). They're also eukaryotic, meaning their cell nuclei are enclosed in membranes, unlike prokaryotic bacteria. They live in water (or watery tissues within the body, in the case of some diseases) and are classified in their own kingdom. You might have heard of some of these protists before: amoeba, euglena, paramecium, dinoflagellates, slime mold, and even most algae. You can either collect your own pond water to study, or use a culture kit.
If you are using a protozoa culture kit, protists will usually begin to appear after 24 hours with the most variety after about 3 days. Different creatures will grow at different depths of your cup of water, so take samples from different parts of the cup.
Type of movement: Protozoa use different methods of locomotion and are usually categorized based on how they move. An amoeba uses slow amoeboid movement, flowing along with pseudopods, or temporary foot-like extensions. One part of its cell wall flows out, looking like a foot, and then pulls the rest of the amoeba after it. (This is also the way the white blood cells in our bodies move.) Creatures like a euglena move with fast flagellate movement. They propel themselves with one or two whip-like flagella. Other protists, like paramecium, use ciliate movement. They are covered with tiny hair-like threads called cilia that beat back and forth rhythmically, propelling them through water. Flagella and cilia can be hard to see—try reducing the light entering the microscope and increasing the magnification.
Eating method: Eating habits amongst protozoans vary, too. Some protists, such as euglena or volvox (a type of algae), use chloroplasts to generate energy through photosynthesis, similar to plants. Euglena also serve as decomposers, by feeding off dead organisms. The amoeba, on the other hand, engulfs its prey with its pseudopodia and brings the food into its food vacuole (a sac where food is stored until digested). A paramecium sweeps its food down an oral groove lined with cilia into a gullet that closes off when full and becomes a food vacuole.