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The concept of a "tree" serves as an efficient way to represent relationships between languages and language splits. It also serves as a way of testing hypotheses about the connections and ages of language families. For example, relationships among languages can be shown by using cognates as characters.
A phylogenetic tree, phylogeny or evolutionary tree is a graphical representation which shows the evolutionary history between a set of species or taxa during a specific time. [ 1 ] [ 2 ] In other words, it is a branching diagram or a tree showing the evolutionary relationships among various biological species or other entities based upon ...
The cladistic or phylogenetic species concept is that a species is the smallest lineage which is distinguished by a unique set of either genetic or morphological traits. No claim is made about reproductive isolation, making the concept useful also in palaeontology where only fossil evidence is available.
The science that tries to reconstruct phylogenetic trees and thus discover clades is called phylogenetics or cladistics, the latter term coined by Ernst Mayr (1965), derived from "clade". The results of phylogenetic/cladistic analyses are tree-shaped diagrams called cladograms; they, and all their branches, are phylogenetic hypotheses. [12]
The term monophyly, or monophyletic, derives from the two Ancient Greek words μόνος (mónos), meaning "alone, only, unique", and φῦλον (phûlon), meaning "genus, species", [4] [5] and refers to the fact that a monophyletic group includes organisms (e.g., genera, species) consisting of all the descendants of a unique common ancestor.
Phylogenetic diversity is a measure of biodiversity which incorporates phylogenetic difference between species. It is defined and calculated as "the sum of the lengths of all those branches that are members of the corresponding minimum spanning path ", [ 1 ] in which 'branch' is a segment of a cladogram , and the minimum spanning path is the ...
Molecular phylogenetics (/ m ə ˈ l ɛ k j ʊ l ər ˌ f aɪ l oʊ dʒ ə ˈ n ɛ t ɪ k s, m ɒ-, m oʊ-/ [1] [2]) is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships.
From the perspective of ancestry, clades are simple to define in purely phylogenetic terms without reference to clades previously introduced: a node-based clade definition, for example, could be "All descendants of the last common ancestor of species X and Y". On the other hand, polyphyletic groups can be delimited as a conjunction of several ...