A Euglena

Protista is a very large and diverse kingdom of eukaryotic organisms.  Protists have existed from the Neoproterozoic era to today.  This is a very interesting kingdom because the organisms are not all related through evolution.  The group is mainly divided into protozoa (animal-like protists), protophyta (mostly unicellular algae), slime molds, and water molds. 

This kingdom is essentially reserved for organisms that do not fit into any other kingdom, and therefore are not related to each other. For example, the criteria for being an animal is to be a multicellular heterotrophic organism that can move. If an organism fills every description except being autotrophic, then it will be classified as a protist.