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. In biology, Phylogenetics (Greek: phylon = race and genetic = birth) is the taxonomical classification of organisms based on how closely they are related in terms of evolutionary differences. ... A taxon (plural taxa) is an element of a taxonomy, e. ...

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 genetic grouping. A warm-blooded (homeothermic) animal is one that can keep its core body temperature at a nearly constant level regardless of the temperature of the surrounding environment (that is, to maintain thermal homeostasis) . This can involve not only the ability to generate heat, but also the ability to cool down... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary... For other meanings of bird, see bird (disambiguation). ...

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. Scientific classification or biological classification is how biologists group and categorize extinct and living species of organisms. ... In biology, a species is, loosely speaking, a group of related organisms that share a more or less distinctive form and are capable of interbreeding. ...

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. In phylogenetics, a group is monophyletic (Greek: of one stem) if all organisms in that group are known to have developed from a common ancestral form, and all descendants of that form are included in the group. ... This cladogram shows the relationship among various insect groups. ... Paraphyletic - Wikipedia /**/ @import /skins-1. ...