AP BIOLOGY

Detailed explanation-1: -Common descent is an effect of speciation, in which multiple species derive from a single ancestral population. The more recent the ancestral population two species have in common, the more closely are they related.

Detailed explanation-2: -Loosely, a monophyletic taxon is one that includes a group of organisms descended from a single ancestor, whereas a polyphyletic taxon is composed of unrelated organisms descended from more than one ancestor.

Detailed explanation-3: -The last universal common ancestor (LUCA) is the most recent population from which all organisms now living on Earth share common descent-the most recent common ancestor of all current life on Earth.

Detailed explanation-4: -Ancestral organism shared by two or more descendent lineages-in other words, an ancestor that they have in common.

Detailed explanation-5: -If a group of organisms is believed to have shared a common ancestor, the group containing that ancestor and all of its descendants is called a monophyletic group. A monophyletic group must be recognized by the presence of at least one shared derived character.