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:7/11/2014)... Mineral Research awarded Michael F. Holick, PhD, MD, of ... Louis V. Avioli Award. Holick, a professor of medicine, ... revolutionizing the understanding of vitamin D and its role ... member of the American Society for Bone and Mineral ... basic research. It is named for ASBMR,s first president ...
(Date:7/11/2014)... of Standards and Technology (NIST) need a special ... often prove that necessity is truly the mother ... M. Lorna De Leoz and Stephen Stein, NIST ... Glycomics is the study of the abundant, often-branched ... proteins and lipids and influence cellular processes, including ...
(Date:7/11/2014)... the Max Planck Institute for Medical Research in Heidelberg, ... photosynthesis, the process by which the Earth first gained ... which is therefore crucial for all higher forms of ... first direct visualization of a crucial event in the ... protein complex, photosystem II, splits water into hydrogen and ...
Breaking Biology News(10 mins):BUSM's Michael F. Holick receives American Society for Bone and Mineral Research award 2A first direct glimpse of photosynthesis in action 2
... clinical trial of a recombinant vaccine for the deadly ... indicate the vaccine is safe and effective in eliciting ... , The nearly year-long pilot study involved three groups ... a series of three injections of various doses of ...
... Researchers at the San Francisco VA Medical Center have uncovered ... grow in response to blocked arteries. , A team led ... in mice that the MMP2 gene is essential for the ... blocked. , The team also identified and described, for ...
... Researchers at the U.S. Department of Energy's Brookhaven National ... browser and database of the brain of a popular ... around the world can now download these extremely accurate ... -- such as which parts of the brain are ...
Cached Biology News:Human trial proves ricin vaccine safe, induces neutralizing antibodies; further tests planned 2Human trial proves ricin vaccine safe, induces neutralizing antibodies; further tests planned 3Human trial proves ricin vaccine safe, induces neutralizing antibodies; further tests planned 4Genetic key to growth of new arteries is identified 2Genetic key to growth of new arteries is identified 3
Other biology definitionOther Tags