Arbres phylogéniques

Phylogenetic trees show the evolutionary relationships among organisms. These relationships are shown in a branching diagram with tips, branches, nodes, and a root.

The tips generally represent species, also called taxa. The branches trace evolutionary change, such as changes in DNA sequences or the evolution of new traits like feathers.

When two groups share a recent common ancestor, they are called sister taxa. The point where branches meet is called a node and represents a common ancestor. The root of the tree represents the common ancestor shared by all taxa shown in the tree.

Phylogenetic trees show the evolutionary relationships among organisms based on common ancestry.

A group that includes a common ancestor and all of its descendants is called a clade, or a monophyletic group. For example, all birds belong to the bird clade.

A paraphyletic group includes a common ancestor but not all of its descendants. For example, reptiles are often considered paraphyletic when birds are excluded, even though birds evolved from reptile ancestors.

A polyphyletic group includes organisms whose most recent common ancestor is not included in the group. For example, older classifications group