Overview
Protists are any eukaryotes that don't belong to the previous three kingdoms in this profile: plants, animals, or fungi[1]. Since this leaves a paraphyletic group, there is immense diversity among protists, however most are single cellular or otherwise small[2, p575]. Consequently, this also includes near ancestors to the eukaryotic kingdoms, and some of the entries will focus on these relatives of plants, animals and fungi.
Here's an overview of hypothesized protist divisions and relations[1]:
Here's an overview of hypothesized protist divisions and relations[1]:
References
[1]http://tolweb.org/tree/home.pages/glossary.html
[2]Campbell & Reece, Biology, 8th Edition
[2]Campbell & Reece, Biology, 8th Edition