Protist both microbial eukaryotes and macroscopic organisms that do not fit into the other traditional kingdoms. In cladistic systems (classifications based on common ancestry), there are no equivalents to the taxa Protista or Protoctista, both terms referring to a paraphyletic group that spans the entire eukaryotic tree of life. In cladistic classification, the contents of Protista are distributed among various "supergroups" (SAR, such as protozoa and some algae, Archaeplastida, such as land plants and some algae, Excavata, which are a group of unicellular organisms, and Opisthokonta, such as animals and fungi, etc.). "Protista", <nowiki>"Protoctista"</nowiki> and "Protozoa" are considered obsolete. However, the
Virus classification refining, and maintaining a universal virus taxonomy. The system shares many features with the classification system of cellular organisms, such as taxon structure. However, this system of nomenclature differs from other taxonomic codes on several points. A minor point is that names of orders and families are italicized, unlike in the International Code of Nomenclature for algae, fungi, and plants and International Code of Zoological Nomenclature. Viral classification starts at the level of realm and continues as follows, with the taxon suffixes given in italics: Species names often take the form of "[Disease] virus", particularly for higher plants and animals.