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Information about Polyphyletic

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The group of "warm blooded animals" is polyphyletic.
In phylogenetics, a taxon is polyphyletic (Greek for "of many races") if the trait its members have in common evolved separately in different places in the phylogenetic tree. Equivalently, a polyphyletic taxon does not contain the most recent common ancestor of all its members.

For example, the group of warm-blooded animals is polyphyletic, because it contains both mammals and birds, but the most recent common ancestor of mammals and birds was cold-blooded. Warm-bloodedness evolved separately in the ancestors of mammals and the ancestors of birds, so it is not a true phylogenetic grouping.

Scientific classification aims to group species together such that every group is descended from a single common ancestor, and the elimination of groups that are found to be polyphyletic is therefore a common goal, and is often the stimulus for major revisions of the classification schemes. A polyphyletic group can be "fixed" either by excluding clades or by adding the common ancestor.

Opinions differ as to whether valid groups need to contain all the descendants of a common ancestor. Groups that do so are called monophyletic, and according to cladistics it should be the aim of classification to ensure that all groups have this property. However, many other taxonomists would argue that there is a valid place for groups that are paraphyletic, i.e. contain only the descendants of a common ancestor, but do not contain all its descendants.

References

  • Colin Tudge (2000). The Variety of Life. Oxford University Press. ISBN 0198604262.2000&rft.pub=Oxford%20University%20Press"> 
phylogenetics (Greek: phyle = tribe, race and genetikos = relative to birth, from genesis = birth) is the study of evolutionary relatedness among various groups of organisms (e.g., species, populations).
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For the journal, see .
A taxon (plural taxa), or taxonomic unit, is a name designating an organism or group of organisms. A taxon is assigned a rank and can be placed at a particular level in a systematic hierarchy reflecting evolutionary
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Greek}}} 
Writing system: Greek alphabet 
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Warm-blooded animals maintain thermal homeostasis; that is, they keep their body temperature at a constant level. This involves the ability to cool down or produce more body heat. Warm-blooded animals mainly control their body temperature by regulating their metabolic rates (e.g.
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Mammalia
Linnaeus, 1758

Subclasses & Infraclasses
  • Subclass †Allotheria*
  • Subclass Prototheria
  • Subclass Theria

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Aves
Linnaeus, 1758

Orders

About two dozen - see section below

Birds (class Aves) are bipedal, warm-blooded, egg-laying vertebrate animals.
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Scientific classification or biological classification is a method by which biologists group and categorize species of organisms. Scientific classification also can be called scientific taxonomy, but should be distinguished from folk taxonomy, which lacks scientific basis.
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species is one of the basic units of biological classification. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring.
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In phylogenetics, a group is monophyletic (Greek: "of one race") if it consists of an inferred common ancestor and all its descendants. A taxonomic group that contains organisms but not their common ancestor is called polyphyletic, and a group that contains some but not all
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Cladistics is a philosophy of classification that arranges organisms only by their order of branching in an evolutionary tree and not by their morphological similarity, in the words of Luria et al. (1981).
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In phylogenetics, a group of organisms is said to be paraphyletic (Greek para = near and phyle = race) if the group contains its most recent common ancestor, but does not contain all the descendants of that ancestor.
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Colin Tudge (born 22 April 1943) is a British science writer. A biologist by training, he is the author of numerous works on food, agriculture, genetics, and species diversity.
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