Editing Phylogenetic tree (section)

{{short description|Branching diagram of evolutionary relationships between organisms}}
{{distinguish|text= [[Philogyny]], the fondness, love or admiration of women}}
{{Evolutionary biology}}

A '''phylogenetic tree''', '''phylogeny''' or '''evolutionary tree''' is a graphical representation which shows the [[evolution]]ary history between a set of [[species]] or [[Taxon|taxa]] during a specific time.<ref name=":0">{{Cite book |last=Khalafvand |first=Tyler |url=https://books.google.com/books?id=uEDEtwEACAAJ |title=Finding Structure in the Phylogeny Search Space |date=2015 |publisher=Dalhousie University |language=en}}</ref><ref name="Felsenstein">Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.</ref> In other words, it is a branching [[diagram]] or a [[tree (graph theory)|tree]] showing the evolutionary relationships among various biological species or other entities based upon similarities and differences in their physical or genetic characteristics. In evolutionary biology, all life on Earth is theoretically part of a single phylogenetic tree, indicating [[common ancestry]]. [[Phylogenetics]] is the study of phylogenetic trees. The main challenge is to find a phylogenetic tree representing optimal evolutionary ancestry between a set of species or taxa. [[computational phylogenetics|Computational phylogenetics (also phylogeny inference)]] focuses on the algorithms involved in finding optimal phylogenetic tree in the phylogenetic landscape.<ref name=":0" /><ref name="Felsenstein" />

Phylogenetic trees may be rooted or unrooted. In a ''rooted'' phylogenetic tree, each node with descendants represents the inferred [[most recent common ancestor]] of those descendants,<ref>{{Cite journal |last1=Kinene |first1=T. |last2=Wainaina |first2=J. |last3=Maina |first3=S. |last4=Boykin |first4=L. |date=21 April 2016 |title=Rooting Trees, Methods for |journal=Encyclopedia of Evolutionary Biology |pages=489–493 |doi=10.1016/B978-0-12-800049-6.00215-8 |pmc=7149615 |isbn=9780128004265 }}</ref> and the edge lengths in some trees may be interpreted as time estimates. Each node is called a taxonomic unit. Internal nodes are generally called hypothetical taxonomic units, as they cannot be directly observed. Trees are useful in fields of biology such as [[bioinformatics]], [[systematics]], and [[phylogenetics]]. ''Unrooted'' trees illustrate only the relatedness of the [[leaf nodes]] and do not require the ancestral root to be known or inferred.