Modern Systematics. Traditional Systematics Scientists have traditionally used similarities in appearance and structure to group organisms. However, this approach has been problematic. Some groups look similar but turn out to be distantly related.
Are these groups related?
Fossil evidence now shows that birds are considered part of the “family tree” of dinosaurs.
This family tree, or phylogenetic tree, represents a hypothesis of the relationships between several groups
Evidence of Order and Time
DNA mutations occur at relatively constant rates, so they can be used as an approximate “genetic clock.”
Scientists can measure the genetic differences between taxa and estimate time of divergence.
Inference Using Parsimony