Cladogram of life on Earth, illustration. Cladistics is a system of biological classification in which organisms are categorized in groups (clades) based on the most recent common ancestor. The resulting relationship between groupings is known as a cladogram. This cladogram shows all life on Earth arising from a shared origin of life (bottom). The main groupings are: prokaryotes, eukaryotes, multi-cellular organisms, plants and animals. The path from animals to primates (which includes humans) passes through vertebrates, mammals, and placental mammals.