The protista

The protista are a paraphyletic group of organisms that are not animals, true fungi or green plants. There are approximately 200 000 named species. Traditionally they were classified into nonmonophyletic, adaptive groups called the flagellates, algae, and protozoa. There are about 80 different patterns of organization, clustered into 60 lineages.

The major groups at the root of the Tree of Life are under review.  Our previous under- standing of the monophyly of the Archaea, and the place of the amitochondrial protists at the base of the eukaryotic branch, has been shown to be untenable. The supergroup view

                           Figure:  Tentative phylogenetic tree of the probable evolutionary sequence of protistan microbes.

is favored, where there are  currently proposed up  to five large,  structurally and  meta- bolically diverse, groups of microorganisms. Some supergroups have good supporting evidence, others less so. Again the Tree Of Life website provides an excellent discussion of current views.