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Phylum

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In biology, a phylum (/ˈfaɪləm/; plural: phyla)[note 1] is a taxonomic rank below kingdom and above class.

Traditionally, in botany the term division is used instead of "phylum", although in 1993 the International Botanical Congress accepted the designation "phylum".[1][2] The kingdom Animalia contains approximately 35 phyla; the kingdom Plantae contains 12 phyla. Current research in phylogenetics is uncovering the relationships between phyla, which are contained in larger clades, like Ecdysozoa and Embryophyta. Phylum. General description and familiar examples[edit] The definitions of zoological phyla have changed importantly[clarification needed] from their origins in the six Linnaean classes and the four "embranchements" of Georges Cuvier.[3] Haeckel introduced the term phylum, based on the Greek word phylon.

Phylum

In plant taxonomy, Eichler (1883) classified plants into five groups, named divisions.[5] Definition based on genetic relation[edit] This changeability of phyla has led some biologists to call for the concept of a phylum to be abandoned in favour of cladistics, a method in which groups are placed on a "family tree" without any formal ranking of group size.[7] Definition based on body plan[edit] A definition of a phylum based on body plan has been proposed by paleontologists Graham Budd and Sören Jensen (as Haeckel had done a century earlier).

This approach brings some small problems—for instance, ancestral characters common to most members of a phylum may have been lost by some members.

General description and familiar examples

Lists of Phyla. Cladistics. Cladistics (from Greek κλάδος, klados, i.e.

Cladistics

"branch")[1] is an approach to biological classification in which organisms are grouped together based on whether or not they have one or more shared unique characteristics that come from the group's last common ancestor and are not present in more distant ancestors. Therefore, members of the same group are thought to share a common history and are considered to be more closely related.[2][3][4][5] The original methods used in cladistic analysis and the school of taxonomy derived from it originated in the work of the German entomologist Willi Hennig, who referred to it as phylogenetic systematics (also the title of his 1966 book); the use of the terms "cladistics" and "clade" was popularized by other researchers. Cladistics in the original sense refers to a particular set of methods used in phylogenetic analysis, although it is now sometimes used to refer to the whole field.

Phylogenetics. In biology, phylogenetics /faɪlɵdʒɪˈnɛtɪks/ is the study of evolutionary relationships among groups of organisms (e.g. species, populations), which are discovered through molecular sequencing data and morphological data matrices.

Phylogenetics

The term phylogenetics derives from the Greek terms phylé (φυλή) and phylon (φῦλον), denoting "tribe", "clan", "race"[1] and the adjectival form, genetikós (γενετικός), of the word genesis (γένεσις) "origin", "source", "birth". In fact, phylogenesis is the process, phylogeny is science on this process, and phylogenetics - phylogeny which is based on analysis of sequences of biological macromolecules (DNA, RNA and proteins, in the first).[2] The result of phylogenetic studies is a hypothesis about the evolutionary history of taxonomic groups: their phylogeny.[3] Construction of a phylogenetic tree[edit] Prior to 1990, phylogenetic inferences were generally presented as narrative scenarios. Such methods are legitimate, but often ambiguous and hard to test.[6][7][8]

Systematics. A comparison of phylogenetic and phenetic concepts Biological systematics is the study of the diversification of living forms, both past and present, and the relationships among living things through time.

Systematics

Relationships are visualized as evolutionary trees (synonyms: cladograms, phylogenetic trees, phylogenies). Phylogenies have two components, branching order (showing group relationships) and branch length (showing amount of evolution). Phylogenetic trees of species and higher taxa are used to study the evolution of traits (e.g., anatomical or molecular characteristics) and the distribution of organisms (biogeography). Systematics, in other words, is used to understand the evolutionary history of life on Earth. Definition and relation with taxonomy[edit] John Lindley is probably the first to define systematics, in 1830, although he used “systematic botany” instead of using the term “systematics” directly.[1]

Taxonomy (biology) Taxonomy (from Ancient Greek: τάξις taxis, "arrangement," and -νομία -nomia, "method")[1] is the science of defining groups of biological organisms on the basis of shared characteristics and giving names to those groups.

Taxonomy (biology)

Organisms are grouped together into taxa (singular: taxon) and given a taxonomic rank; groups of a given rank can be aggregated to form a super group of higher rank and thus create a taxonomic hierarchy.[2][3] The Swedish botanist Carolus Linnaeus is regarded as the father of taxonomy, as he developed a system known as Linnaean classification for categorization of organisms and binomial nomenclature for naming organisms. With the advent of such fields of study as phylogenetics, cladistics, and systematics, the Linnaean system has progressed to a system of modern biological classification based on the evolutionary relationships between organisms, both living and extinct.