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
Bacteria of the archaea and eukaryotes. Here, eukaryotes resulted from the entering of ancient bacteria into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves possibly related to the Archaea. This involved the engulfment by proto-eukaryotic cells of alphaproteobacterial symbionts to form either mitochondria or hydrogenosomes, which are still found in all known Eukarya (sometimes in highly reduced form, e.g. in ancient "amitochondrial" protozoa). Later, some eukaryotes that already contained mitochondria also engulfed cyanobacteria-like organisms, leading to the formation of chloroplasts in algae and plants. This is known as secondary endosymbiosis. Bacteria display a wide diversity of shapes and