Prior to scientific study of evolution and species ancestry, living things were grouped according to the Linnaean system of classification that followed the hierarchy of: kingdom, phylum, class, order, family, genus, and species. It was based purely on the physical and macroscopic descriptions of an organism. However, based on modern understanding of genetics, scientists have developed an alternative approach for classifying species on evolution trees. This type of classification is called phylogenetic classification. Phylogenetic classification only classifies species by clades (that is, groups of organisms that are descendants of a common ancestor). For example, in a Linnaean system, birds and non-avian dinosaurs may be placed into two separate groups while in a phylogenetic classification, they both belong to the same group as they are from the same lineage.
The following example considers reptiles and birds. It is important to note that 'reptiles' would not be a correct phylogenetic classification, as this classification would exclude birds.
Click the boxes to see which species are grouped in the following phylogenetic classifications.
