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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).
This process is also known as stratified sampling or clade-based sampling. [18] The practice occurs given limited resources to compare and analyze every species within a target population. [17] Based on the representative group selected, the construction and accuracy of phylogenetic trees vary, which impacts derived phylogenetic inferences. [18]
Under phylogenetic taxonomy, amphibians do not constitute a monophyletic group in that the amniotes (reptiles, birds and mammals) have evolved from an amphibian ancestor and yet are not considered amphibians. Such paraphyletic groups are rejected in phylogenetic nomenclature, but are considered a signal of serial descent by evolutionary ...
In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon , but not found in any others or outgroup taxa , not even those most closely related to the focal taxon (which may be a species , family or in general any clade). [ 2 ]
Listing all these organisms (i.e. providing a full circumscription) requires the complete phylogenetic tree to be known. In practice, there are almost always one or more hypotheses as to the correct relationship. Different hypotheses result in different organisms being thought to be included in the named taxon, but application to the name in ...