Which are the groups of living beings that form the protist kingdom?
The protist kingdom contains protozoans and algae. (Two groups of fungi with same characteristics to protozoans, myxomycetes and oomycetes, have been divided as protists.)
Unicellular protozoans and algae are unicellular eukaryotes. The pluricellular algae are eukaryotes of easy structure too. It is believed that protists are phylogenetic ancestors of living beings of the other eukariotic kingdoms (fungi, plants and animals).
Protists Review - Image Diversity: protozoan algae