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The term paraphyly, or paraphyletic, derives from the two Ancient Greek words παρά (pará), meaning "beside, near", and φῦλον (phûlon), meaning "genus, species", [2] [3] and refers to the situation in which one or several monophyletic subgroups of organisms (e.g., genera, species) are left apart from all other descendants of a unique common ancestor.
A paraspecies (a paraphyletic species) is a species, living or fossil, that gave rise to one or more daughter species without itself becoming extinct. [1] Geographically widespread species that have given rise to one or more daughter species as peripheral isolates without themselves becoming extinct (i.e. through peripatric speciation) are examples of paraspecies.
An evolutionary grade is a group of species united by morphological or physiological traits, that has given rise to another group that has major differences from the ancestral group's condition, and is thus not considered part of the ancestral group, while still having enough similarities that we can group them under the same clade.
A paraphyletic assemblage is one that is constructed by taking a clade and removing one or more smaller clades. [32] Removing one clade produces a singly paraphyletic assemblage, removing two produces a doubly paraphyletic assemblage, and so on.) [ 33 ]
Fishes are a paraphyletic group and for this reason, the class Pisces seen in older reference works is no longer used in formal taxonomy.Traditional classification divides fish into three extant classes (Agnatha, Chondrichthyes, and Osteichthyes), and with extinct forms sometimes classified within those groups, sometimes as their own classes: [1]
A clade is by definition monophyletic, meaning that it contains one ancestor which can be an organism, a population, or a species and all its descendants. [ note 1 ] [ 10 ] [ 11 ] The ancestor can be known or unknown; any and all members of a clade can be extant or extinct.
A stem group is a paraphyletic assemblage composed of the members of a pan-group or total group, above, minus the crown group itself (and therefore minus all living members of the pan-group). This leaves primitive relatives of the crown groups , back along the phylogenetic line to (but not including) the last common ancestor of the crown group ...
The wasps are a cosmopolitan paraphyletic grouping of hundreds of thousands of species, [1] [2] consisting of the narrow-waisted clade Apocrita without the ants and bees. [3] The Hymenoptera also contain the somewhat wasplike but unwaisted Symphyta , the sawflies.