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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.
In biological phylogenetics, a clade (from Ancient Greek κλάδος (kládos) 'branch'), also known as a monophyletic group or natural group, [1] is a grouping of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. [2]
A rooted tree of life into three ancient monophyletic lineages: bacteria, archaea, and eukaryotes based on rRNA genes Lineages are typically visualized as subsets of a phylogenetic tree . A lineage is a single line of descent or linear chain within the tree, while a clade is a (usually branched) monophyletic group, containing a single ancestor ...
The idea of a tree of life arose from ancient notions of a ladder-like progression from lower into higher forms of life (such as in the Great Chain of Being).Early representations of "branching" phylogenetic trees include a "paleontological chart" showing the geological relationships among plants and animals in the book Elementary Geology, by Edward Hitchcock (first edition: 1840).
Monophyletic phylogenetic tree of organisms". [23] Phylogenetic nomenclature is a semantic extension of the general acceptance of the idea of branching during the course of evolution, represented in the diagrams of Jean-Baptiste Lamarck and later writers like Charles Darwin and Ernst Haeckel.
A taxon is called monophyletic if it includes all the descendants of an ancestral form. [61] [62] Groups that have descendant groups removed from them are termed paraphyletic, [61] while groups representing more than one branch from the tree of life are called polyphyletic.
The two approaches, evolutionary taxonomy and the phylogenetic systematics derived from Willi Hennig, differ in the use of the word "monophyletic". For evolutionary systematicists, "monophyletic" means only that a group is derived from a single common ancestor.
These relationships are determined by phylogenetic inference methods that focus on observed heritable traits, such as DNA sequences, protein amino acid sequences, or morphology. The result of such an analysis is a phylogenetic tree—a diagram containing a hypothesis of relationships that reflects the evolutionary history of a group of ...