protists are the 'leftover' organisms that cannot be determined if they belong to the other kingdoms. They might be unicellular, some form colonies, some are pseudopods such as ameba, and some could cause malaria when introduced by the mosquito. They evolved from the archae bacteria since they're more closely related. We have concluded (partially) that there are 10 kingdoms under which the protist fall into depending on what's their niche and how they resemble.
Examples: Ulva and Zooflagellate