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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]
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.
A clade, a monophyletic taxon, is a taxon that consists of the last common ancestor and all its descendants. [31] A clade is characterized by one or more apomorphies: derived character states present in the first member of the taxon, inherited by its descendants (unless secondarily lost), and not inherited by any other taxa. Paraphyly
However, the ancestors of mammals and birds also had these traits and so birds and mammals can be said to "have evolved from reptiles", making the reptiles, when defined by these traits, a grade rather than a clade. [4] In microbiology, taxa that are thus seen as excluded from their evolutionary grade parent group are called taxa in disguise. [5]
It is applied to a clade, a monophyletic group, which includes most of the (former) dicots. [ citation needed ] "Tricolpate" is a synonym for the " Eudicot " monophyletic group, the "true dicotyledons " (which are distinguished from all other flowering plants by their tricolpate pollen structure).
The diagram shows three common ways of doing this. For previously defined clades A, B, and C, the clade X can be defined as: The three most common ways to define the name of a clade: node-based, branch-based and apomorphy-based definition. The tree represents a phylogenetic hypothesis of the relations of A, B and C.
The three-domain system adds a level of classification (the domains) "above" the kingdoms present in the previously used five- or six-kingdom systems.This classification system recognizes the fundamental divide between the two prokaryotic groups, insofar as Archaea appear to be more closely related to eukaryotes than they are to other prokaryotes – bacteria-like organisms with no cell nucleus.
They are widely used in the pharmaceutical, cosmetic, food, and textile sectors. They also have interesting therapeutic properties; for example gum arabic is antitussive and anti-inflammatory . [ medical citation needed ] The most well known gums are tragacanth ( Astragalus gummifer ), gum arabic ( Acacia senegal ) and guar gum ( Cyamopsis ...