Understanding Paraphyly in Biology: Definition and Examples

paraphyletic

In biology, a paraphyletic group, or paraphyly, refers to a taxonomic group that consists of some, but not all, of the descendants of a common ancestor

In biology, a paraphyletic group, or paraphyly, refers to a taxonomic group that consists of some, but not all, of the descendants of a common ancestor. This means that a paraphyletic group includes a common ancestor and some of its descendants, but not all of them. The term “paraphyly” comes from the Greek words “para,” meaning “beside,” and “phylon,” meaning “tribe” or “race.”

A paraphyletic group is usually formed when a taxonomic group is defined based on some, but not all, characteristics derived from a common ancestor. These characteristics may be shared by some members of the group but not by all. This leads to the exclusion of certain descendants that have evolved additional characteristics or undergone significant evolutionary changes.

For example, let’s consider the class Reptilia. Traditionally, reptiles were defined as a paraphyletic group consisting of lizards, snakes, turtles, and crocodiles. Birds, which descended from within this group, were not included. However, based on cladistic analysis and new evolutionary evidence, birds are now considered the descendants of ancestral reptiles, making Reptilia a monophyletic group that includes both birds and reptiles.

The concept of paraphyly has become less favored in modern taxonomy, as the scientific community generally prefers monophyletic groups. Monophyly refers to taxonomic groups that include all descendants of a common ancestor and are based on shared derived characteristics, known as synapomorphies. Monophyletic groups are considered more precise and accurate in reflecting the evolutionary relationships among organisms.

In summary, paraphyly is a term used in biology to describe a taxonomic group that includes some, but not all, descendants of a common ancestor. This concept has become less favored in modern taxonomy as scientists strive to use monophyletic groups that include all descendants and are based on shared derived characteristics.

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