Derived Describes a character state that is present in one or more subclades, but not all, of a clade under consideration. A derived character state is inferred to be a modified version of the primitive condition of that character, and to have arisen later in the evolution of the clade. When one organism takes up permanent residence within another, such that the two become a single functional organism. Mitochondria and plastids are believed to have resulted from endosymbiosis. Evolution Change through time.
Organic evolution is descent with modification.
Evolutionary tree A branching diagram depicting the genealogical relationships of taxa in time. The points at which lineages split represent ancestors to the taxa at the terminal points of the tree. Several evolutionary trees may be consistent with a single cladogram. When all the members of a lineage or taxon die, the group is said to be extinct. Extinction is irreversible.