Introduction to Protista

Kingdom Protista, sometimes known as the "messy kingdom," includes all eukaryotic organisms that can't be placed in the plant, animal, or fungi kingdom. Really, the only thing Protista have in common is their simple organization, which separates them from the other kingdoms. The kingdom itself is divided into subdivisions based on what other kingdom (plant, animal, or fungi) the organism was most similar to. An example would be protozoans, which are the animal-like Protista, characterized by movement and being heterotrophs. Some protozoans are flagellates (Giardia lamblia) and amoeboids (Entamoeba histolytica).

In the 1830s, Georg August Goldfuss, a German biologist, first separated Protista from other organisms, starting with ciliates and corals. In 1845 it was enlarged to include all unicellular animals, and in 1860, John Hogg proposed and Ernest Haeckel got Protista to be the taxon of primitive forms. In 1939, Herbert Copeland argued that Haeckel's version of Protista included prokaryotes and Hogg's didn't. Copeland described Protista as "nucleated eukaryotes." Later the kingdom Protista was separated into two groups: Protista and Monera. Protista included eukaryotic microorganisms and Monera took prokaryotes.