These are the creatures that form the food of most other marine animals. Creatures from the small shrimp-like krill, to the largest animal in the world, the blue whale, make a feast of these microscopic critters. Also this is how the suns energy enters into the marine food chain. Movement for protozoans is mainly achieved by one of three body parts, flagella, cilia, pseudopodia. These body parts are one of the ways scientists classify these organisms.
Flagella are long hair-like structures that look like a tail.
Movement through water is achieved by circular rotation of the flagellum at its base similar to a propeler on a boat. Cilia are usually present in groups. When viewed under a microscope a pseudopodium may resemble a tentacle. Listed below is a partial classification of the protozoan invertebrates. More may come if the demand warrants the space.