系統図

Phylogeny describes the ancestral relationships between organisms. The connections often take the form of a tree called the Phylogenetic tree, with tips, branches, nodes —points where branches meet, and roots.

The phylogenetic tree represents evolutionary relationships inferred from morphological or molecular data.

The tips of the tree generally represent extant or living taxa.

The branches represent evolutionary changes between ancestors and descendants, such as a change in the DNA sequence or the evolution of a characteristic, like feathers.

Species that share an immediate common ancestor —sister taxa, share nodes, like reptiles and birds. These are each other's closest relatives.

Rodents and humans share a common ancestor. But it would be wrong to assume that humans evolved from rodents or the other way around.

The node, in this example, represents an extinct common ancestor that was not like a rodent or a human.

The root of the tree represents the most recent common ancestor of all organisms in the tree, such as Metaspriggina in this case.