Navigation Links
Paraphyletic


In phylogenetics, a grouping of organisms is said to be paraphyletic (Greek para = near and phyle = race) if all the members of the group have a common ancestor, but the group does not include all the descendants of the most recent common ancestor of all group members.

Groups which include all the descendants of the most recent common ancestor are commonly termed monophyletic or holophyletic . The former is more common, but sometimes paraphyletic groups are also considered monophyletic, in which case the latter is used.

Many of the older classifications contain paraphyletic groups, especially the traditional 2-6 kingdom systems and the classic division of the vertebrates. For example, the class Reptilia as traditionally defined is paraphyletic because that class does not include two groups of its descendants, birds (in class Aves, birds), and mammals (in class Mammalia). Paraphyletic groups are often erected on the basis of plesiomorphies (ancestral similarities) instead of upon apomorphies (derived similarities).

In most cladistics-based schools of taxonomy, the existence of paraphyletic groups in a classification are regarded as errors. Some groups in currently accepted taxonomies may later turn out to be paraphyletic, in which case the classifications may be revised to eliminate them. Some, however, feel that having paraphyletic groups is an acceptable sacrifice if it makes the taxonomy more understandable. Others argue that paraphyletic groups are necessary to have a comprehensive classification including extinct groups, since each species, genus, and so forth necessarily originates from part of another. It has been suggested that paraphyletic groups should be allowed but clearly marked as such, for instance in the form Reptilia*.

The term paraphyletic is also used in historical linguistics, with similar meaning. For example, centum and satem are papraphyletic groups of Indo-European languages.

References


'"/>


(Date:6/23/2017)... and ITHACA, N.Y. , June 23, ... University, a leader in dairy research, today announced a ... to help reduce the chances that the global milk ... of this dairy project, Cornell University has become the ... the Food Supply Chain, a food safety initiative that ...
(Date:5/16/2017)... , May 16, 2017  Veratad Technologies, LLC ... of online age and identity verification solutions, announced today ... Identity Conference 2017, May 15 thru May 17, 2017, ... Building and International Trade Center. Identity ... globe and in today,s quickly evolving digital world, defining ...
(Date:4/24/2017)... Janice Kephart , former 9/11 ... Partners, LLP (IdSP) , today issues the following ... March 6, 2017 Executive Order: Protecting the ... be instilled with greater confidence, enabling the reactivation ... applications are suspended by until at least July ...
Breaking Biology News(10 mins):
Other biology definition