Editing Clade (section)

{{Short description|Group of a common ancestor and all descendants}}
{{Other uses}}
{{Use dmy dates|date=July 2020}}
[[File:Clade-grade II.svg|thumb|400px| [[Cladogram]] (a branching tree diagram) illustrating the relationships of organisms within groups of taxa known as clades. The vertical line (''stem'') at the base (bottom) represents the [[last common ancestor]]. The blue and orange subgroups are clades, each defined by a common ancestor stem at the base of its respective subgroup (''branch''). The green subgroup alone, however, is ''not'' a clade; it is a [[Paraphyly|paraphyletic group]] relative to the blue subgroup because it excludes the blue branch, which shares the same common ancestor. Together, the green and blue subgroups form a clade.]]

In [[biology]], a '''clade''' ({{etymology|grc|''κλάδος'' (kládos)|branch}}), also known as a '''[[Monophyly|monophyletic]] group''' or '''natural group''',<ref>{{cite book |last1=Martin  |first1=Elizabeth |title=A Dictionary of Biology |last2=Hin |first2=Robert |publisher=Oxford University Press |year=2008}}</ref> is a group of [[organism]]s that is composed of a [[common ancestor]] and all of its descendants.<ref>{{cite book |title=Assembling the Tree of Life |url=https://archive.org/details/assemblingtreeli00crac_335 |url-access=limited |editor-first=Joel |editor-last=Cracraft |editor2-first=Michael J. |editor2-last=Donoghue |chapter=Introduction |page=[https://archive.org/details/assemblingtreeli00crac_335/page/n18 1] |publisher=Oxford University Press |year=2004 |isbn=978-0-19-972960-9}}</ref> Clades are the fundamental unit of [[cladistics]], a modern approach to taxonomy adopted by most biological fields.

The common ancestor may be an individual, a [[population]], or a [[species]] ([[extinct]] or [[Extant taxon|extant]]). Clades are nested, one in another, as each branch in turn splits into smaller branches. These splits reflect [[evolutionary history]] as populations diverged and evolved independently. Clades are termed monophyletic (Greek: "one clan") groups.

Over the last few decades, the cladistic approach has revolutionized biological classification and revealed surprising evolutionary relationships among organisms.<ref name="Palmer-2009">{{Cite book |title=Evolution: The Story of Life |last=Palmer |first=Douglas |publisher=University of California Press |year=2009 |location=Berkeley |pages=13}}</ref> Increasingly, taxonomists try to avoid naming [[Taxon|taxa]] that are not clades; that is, taxa that are not [[Monophyly|monophyletic]]. Some of the relationships between organisms that the molecular biology arm of cladistics has revealed include that [[fungi]] are closer relatives to animals than they are to plants, [[archaea]] are now considered different from [[bacteria]], and multicellular organisms may have evolved from archaea.<ref>{{Cite journal |last=Pace |first=Norman R. |date=2006-05-18 |title=Time for a change |journal=Nature |volume=441 |issue=7091 |pages=289 |bibcode=2006Natur.441..289P |doi=10.1038/441289a |issn=1476-4687 |pmid=16710401|s2cid=4431143 |doi-access=free }}</ref>

The term "clade" is also used with a similar meaning in other fields besides biology, such as [[historical linguistics]]; see [[Cladistics#In disciplines other than biology|Cladistics § In disciplines other than biology]].