Chapter 3 – Protozoa
Publisher Summary 
The goal of this chapter is to provide an introduction to the ecology and classification of protozoa for ecologists who wish to include them in studies of aquatic environments. Protozoa are unicellular or colonial eukaryotes, including all the heterotrophic and motile ones. It is a taxon of convenience. Although the protozoa were considered a single phylum of eukaryotic animals in early classifications, modern treatments distribute the protozoa among many phyla. Large protozoa that have many nuclei, or large amitotic, polyploid nuclei may be best considered acellular rather than unicellular creatures. The chapter focuses on the biology of the animal-like protozoa. It describes the anatomy and morphology at the light-microscope level of different types of protozoa (ciliates, flagellates, amoeboids, and heliozoas), and describes their environmental physiology, ecology, evolution, and taxonomy.