Κλάδος: Διαφορά μεταξύ των αναθεωρήσεων

| page = 217 }}</ref> InThe principle,ancestor thecan ancestor isbe an individualorganism, but in [[Sexual reproduction|sexually reproducingpopulation]] species, there will always be at least two ancestors, and in virtually all instances there will be an influx of genes from the rest of theor [[gene poolspecies]] in the descendant lines. <ref>The individual ancestor is thus often a theoretical construct, and in practical terms the ancestor of a clade of sexually reproducing organisms is a [[speciesPhyloCode]], or[http://www.ohio.edu/phylocode/art1-3.html#chapter1 inChapter the best cases a [[population1]].</ref> The common ancestor of any group of reasonable size and most of that ancestor's descendants have typically been long extinct.<ref group=note>This may not be true in very small and recent clades, where the common ancestor and all descendants are still living.</ref> It is not necessary for a clade to contain any living representatives.