Protozoa are unicellular eukaryotic organisms with animal-like behaviour. Many of them are symbionts, but some of them are parasites, and others are predators of soil bacteria and algae. Protozoa are referred to as animal-like protists because of their movement (motility). However, it is a paraphyletic group; it does not include all the genetic relatives of the group. There isn't an exact definition for protozoa, though it is usually referred to as a unicellular heterotrophic protist, along with amoeba and ciliates.