Diagram showing the evolutionary interrelations of a group of organisms that usually originated from a shared ancestral form.
The ancestor is in the tree trunk; organisms that have arisen from it are placed at the ends of tree branches. The distance of one group from the other groups indicates the degree of relationship; that is, closely related groups are located on branches close to one another. Though phylogenetic trees are speculative, they provide a convenient method for studying phylogenetic relationships and evolution . See also phylogeny .