3. Characteristics The most important protozoans range usually from 10 to 52 micrometers, but can grow as large as 1 mm, and are seen easily by microscope. They were considered formerly to be part of the protista family. Protozoa exist throughout aqueous environments and soil, occupying a range of trophic levels.
4. Classification Protozoa were previously often grouped in the kingdom of Protista, together with the plant-like algae and fungus-like slime molds. As a result of 21st-century systematics, protozoa, along with ciliates, mastigophorans, and apicomplexans, are arranged as animal-like protists. With the possible exception of Myxozoa, protozoa are not categorized as Metazoa. Protozoans are unicellular organisms and are often called the animal-like protists because they subsist entirely on other organisms for food. Most protozoans can move about on their own. Amoebas, Paramecia, and Trypanosomes are all examples of animal-like Protists.
![Protozoa ,[object Object],[object Object]](https://image.slidesharecdn.com/protozoa-110328073540-phpapp02/85/protozoa-1-320.jpg)
