A clade is a systematic classification that includes closely related branches of the evolutionary tree. This method of classification is important in understanding relationships between species that are closely related or have common ancestor. Clades are typically considered to be monophyletic, which contain a species and all of its descendants.
Classifications of TaxonEdit
Organisms can be categorized using different groupings within the evolutionary tree. They can be considered monophyletic, paraphyletic or polyphyletic.
Monophyletic: This type of group contains all of the species within the group that includes the common ancestor. An example of this could be all of the eukaryotes.
Paraphyletic: This group includes the common ancestor, but not all of the recently evolved species. Groupings do not contain all of the descendants of the common ancestor, only some of them. Reptiles have been used as an example, as they gave rise to birds.
Polyphyletic: This group is classified by characteristics and does not include the common ancestor. These species are not related (Carr, 2012). Many evolutionary biologists do not agree with this type of grouping and do not consider it to be natural (Abbey, 1997). An example of this grouping would be flying animals, birds and bats.
Abbey, D. 1997. Graphical explanation of basic phylogenetic terms. Retrieved from: http://www.ucmp.berkeley.edu/glossary/gloss1/phyly.html.
Carr, 2012. Concepts of monophly, polyphyly & paraphyly. Retrieved from: http://www.mun.ca/biology/scarr/Taxon_types.htm.
Yana. 2010. Of terms in Biology: Monophyletic, Paraphyletic…. Retrieved from: http://schaechter.asmblog.org/schaechter/2010/10/of-terms-in-biology-monophyletic-paraphyletic.html.