Κλάδος: Διαφορά μεταξύ των αναθεωρήσεων
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[[File:Clade-grade II.png|thumb|right|334 px|Cladogram (family tree) of a biological group. The red and blue boxes represent ''clades'' (i.e., complete branches). The green box is not a clade, but rather represents an ''[[evolutionary grade]]'', an incomplete group, because the blue clade descends from the
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In biological [[systematics]], a '''clade''' (from [[ancient Greek]] ''{{Polytonic|κλάδος}}'', ''klados'', "branch") signifies a single "branch" on the "[[Tree of life (science)|tree of life]]", a group composed of a single ancestor and all its descendants.<ref>{{cite journal | last=Dupuis | first=Claude | year=1984 | title=Willi Hennig's impact on taxonomic thought | journal=Annual Review of Ecology and Systematics | volume=15 | pages=1–24 | issn=0066-4162}}</ref> The idea that such a "natural group" of organisms should be grouped together and given a [[Taxonomy|taxonomic]] name is central to [[biological classification]]. In [[cladistics]] (which takes its name from the term), clades are the only acceptable units.
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