Protists as Model Organisms for Biology Teaching

Protists are one of the best models of single-celled organisms for use in teaching biology. Free- living species are very common in all fresh- and salt water environments, as well as in soils, whereas some species can be found as parasites or symbionts in large groups of eukaryotes. In this context, we focused on heterotrophic protists, usually known as “protozoa,” which are simple to collect, grow and manipulate. The various protozoa are extraordinarily different in form and activity. These unicellular microscopic organisms carry out all the functions of life within the single cell. They obtain food, digest it, and release indigestible matter from the cell body. They have no nervous system, yet respond to environmental stimuli. They grow, differentiate, have sex, and reproduce. They have no muscles, yet they move in very complex ways. Protozoa perform all of these activities within the small space of the single cell that forms their body. Since all life is made up of cells, the study of protozoa may therefore help students to understand how larger forms of life survive and maintain their health. Using protozoa in the classroom could be a particularly good strategy for explaining and modeling macroscopic processes and systems. What students view through microscope could then be extrapolated into an understanding of their everyday experience.