Clade
Example cladogram : The red and blue groups are clades. The green group is not a clade since it does not include some descendants of the common ancestor of all members shown in green, in this case the blue group. The green and blue groups together form a clade.
A clade (from ancient Greek κλάδος kládos , German 'branch' ), also monophylum , monophyletic group or closed community of descent , is a systematic unit in biology that contains the last common ancestor and all his descendants. This usually describes relationships between different species , but the term can also be applied to individuals . The scientific methodology that deals with clad relationships is cladistics .
If a taxon , i.e. a group of related organisms ( biota ), can be described as a clade, this is thus monophyletic .
- Examples
- Based on a wide range of evidence, it can now be considered certain that the birds descended from the dinosaurs . The dinosaurs as clade must therefore include the birds.
- Due to the descent of humans (genus Homo ), the biota as a taxonomic term (clade) includes humans, the term is then synonymous with living beings.
- Counterexample
- The viruses themselves do not count as living beings. Due to their extremely different genome structure, a polyphyletic origin must be assumed: There is no common ancestor ('original virus') of all viruses, and they therefore do not form clades.
See also
proof
- Neil A. Campbell, Jane B. Reece: Biology . Ed .: Jürgen Markl. 6th edition. Spektrum Akademischer Verlag, Heidelberg, Berlin 2003, ISBN 978-3-8274-1352-9 , pp. 583 .