Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Unrooted trees of three species (human, dog, mouse) display no information about the speciation order (center triplet). Only the use of an outgroup (opossum) places the root on one of the three branches (labeled A, B, and C), giving three possible rooted trees corresponding to the three hypotheses being tested.
