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Related to Sister clade: Cladistic analysis


(klədĭs`tĭks) or

phylogenetic systematics

(fī'lōjənĕt`ĭk), an approach to the classificationclassification,
in biology, the systematic categorization of organisms into a coherent scheme. The original purpose of biological classification, or systematics, was to organize the vast number of known plants and animals into categories that could be named, remembered, and
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 of living things in which organisms are defined and grouped by the possession of one or more shared characteristics (called characters) that are derived from a common ancestor and that were not present in any ancestral group (as envisioned by Charles DarwinDarwin, Charles Robert,
1809–82, English naturalist, b. Shrewsbury; grandson of Erasmus Darwin and of Josiah Wedgwood. He firmly established the theory of organic evolution known as Darwinism.
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's idea of "descent with modification"). Developed by Willi Hennig, a German entomologist, in the 1950s, it is a method of reconstructing evolutionary relationships that emphasizes the importance of descent and common ancestry rather than chronology.

Cladistics places species in a group, or clade, based on a shared character. Within a clade, species that share other characters unique to them are grouped together, and so on, until a cladogram (a branching diagram that resembles a family tree) is assembled. For example, all vertebrates make up a clade; all tetrapods (vertebrates that have four limbs with wrists, ankles, toes, and fingers) form their own clade within the vertebrate clade. In this example the vertebrate clade would be considered "primitive" and the tetrapod clade "derived" or "advanced." In living creatures genetic characters or behaviors as well as more obvious anatomical features might be considered in assembling a cladogram. In paleontologypaleontology
[Gr.,= study of early beings], science of the life of past geologic periods based on fossil remains. Knowledge of the existence of fossils dates back at least to the ancient Greeks, who appear to have regarded them as the remains of various mythological creatures.
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 the characters are necessarily skeletal.

Cladistics is especially significant in paleontology, as it points out gaps in the fossil evidence. It is also felt to be more objective than fossil study, which of necessity extrapolates from a limited number of finds that may or may not be representative of the whole.

See also fossilfossil,
remains or imprints of plants or animals preserved from prehistoric times by the operation of natural conditions. Fossils are found in sedimentary rock, asphalt deposits, and coal and sometimes in amber and certain other materials.
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; datingdating,
the determination of the age of an object, of a natural phenomenon, or of a series of events. There are two basic types of dating methods, relative and absolute.
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Biology a method of grouping animals that makes use of lines of descent rather than structural similarities
References in periodicals archive ?
Goniopholididae is formed by a complex group of basal taxa from the Jurassic and Early Cretaceous of Asia and North America, several putative goniopholidis from the Late Cretaceous of North America and two derived sister clades from the Early to mid-Cretaceous of Europe with Nannosuchus as the basal-most branch (Andrade et al.
Examination of the trees indicates that Micropoltys is always found either at the base of this clade plus its sister clade, or at the base of its sister clade.
In these assays, gene segments of another 31 swine isolates were either SYBR green positive/Cy5 negative (online Technical Appendix Figure 1, yellow) or double negative (online Technical Appendix Figure 1, green), indicating that these virus segments were derived from the sister clade of pandemic (H1N1) 2009 virus or other swine lineages (except NA), respectively.
Specifically, we evaluate the prediction that clades possessing decoupled elements will exhibit increased structural diversity compared to sister clades with coupled systems.
The estimated age of Croton is approximately 55 million years, and the estimated divergence of the Old World clade from its New World sister clade is 40 mya (Fig.
ricketti, which harbors the Chinese sister clade of our coronaviruses, belongs to the same subgenus (Leuconoe Bole) as M.
hecale, are representatives of the sister clade the melpomene-cydno clade, as determined by morphology (Brown 1981) and mtDNA (Brower 1994a), and here provide a plausible root for the melpomene and cydno topology.
The identities of the other members of this sister clade previously sampled for ITS are revised (following Lourteig, 2000) to include O.
cinereus were sister clades and closely related, which is supported by the bootstrap values of 85% (NJ) and 84% (MP).
Our interdisciplinary methodology will combine techniques applied to the study of collective animal behaviour (individual tracking in collective choice and foraging experiments) and neurobiology (immunohistochemistry and neuroanatomical scaling, cytochrome oxidase staining and learning assays) in sister clades of ants that show strong differences in social complexity and thus the relative roles of individual workers and cooperative groups.
Two subordinate or sister clades formed within the major clade of large-spore producing species.
fecunda has four successive sister clades with direct development (two clades of C.