- A phylogenetic tree is a diagram that represents evolutionary relationships among organisms. Phylogenetic trees are hypotheses, not definitive facts.
- The pattern of branching in a phylogenetic tree reflects how species or other groups evolved from a series of common ancestors.
- In trees, two species are more related if they have a more recent common ancestor and less related if they have a less recent common ancestor.
- Phylogenetic trees can be drawn in various equivalent styles. Rotating a tree about its branch points doesn't change the information it carries.