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.
Two extremes of family evolution. Family A is a closed family shown to evolve according to a strict tree-like process, Family B is an open family that evolve by horizontal and vertical evolutionary processes. Its members display family resemblances, as they can be connected through intermediates and relationships of GT homology (see main text).
