A phylogenetic tree or evolutionary tree is a branching diagram or "tree" showing the inferred evolutionary relationships among various biological species or other entities based upon similarities and differences in their physical and/or genetic characteristics. The taxa joined together in the tree are implied to have descended from a common ancestor.
In a rooted phylogenetic tree, each node with descendants represents the inferred most recent common ancestor of the descendants, 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 (HTUs) as they cannot be directly observed. Trees are useful in fields of biology such as bioinformatics, systematics and comparative phylogenetics.
Read more about Phylogenetic Tree: History, Construction, Limitations
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“It is, I fear, but a vain show of fulfilling the heathen precept, “Know thyself,” and too often leads to a self-estimate which will subsist in the absence of that fruit by which alone the quality of the tree is made evident.”
—George Eliot [Mary Ann (or Marian)