Enduring Understanding 1B

Organisms are linked by lines of descent from common ancestry.

Organisms share many conserved core processes and features that are widely distributed among organisms today. These processes provide evidence that all organisms (Archaea, Bacteria, and Eukarya, both extant and extinct) are linked by lines of descent from common ancestry. Elements that are conserved across all domains of life are DNA and RNA as carrier of genetic information, a universal genetic code, and many metabolic pathways. The existenc of these properties in organisms today implies that they were present in a universal ancestor and that present life evolved from a universal ancestor. Phylogenetic trees graphically model evolutionary history and can represent both acquired traits and those lost during evolution.

In eukaryotes, conserved core elements provide evidence for evolution. These features include the presence of a cytoskeleton, a nucleus, membrane-bound organelles, linear chromosomes and endomembrane systems.