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In biology, taxonomy (from Ancient Greek τάξις 'arrangement' and -νομία 'method') is the scientific study of naming, defining (circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon), and these groups are given a taxonomic rank; groups of a given ...
There are no rules for how many species should make a genus, a family, or any other higher taxon (that is, a taxon in a category above the species level). [52] [53] It should be a natural group (that is, non-artificial, non-polyphyletic), as judged by a biologist, using all the information available to them. Equally ranked higher taxa in ...
A simple cladogram showing the evolutionary relationships between four species: A, B, C, and D. Here, Species A is the outgroup, and Species B, C, and D form the ingroup. In cladistics or phylogenetics, an outgroup [1] is a more distantly related group of organisms that serves as a reference group when determining the evolutionary relationships of the ingroup, the set of organisms under study ...
An operational taxonomic unit (OTU) is an operational definition used to classify groups of closely related individuals.The term was originally introduced in 1963 by Robert R. Sokal and Peter H. A. Sneath in the context of numerical taxonomy, where an "operational taxonomic unit" is simply the group of organisms currently being studied. [1]
The hierarchy of biological classification's eight major taxonomic ranks. A genus contains one or more species. Minor intermediate ranks are not shown. A species (pl.: species) is a population of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. [1]
The age of a clade can be described based on two different reference points, crown age and stem age. The crown age of a clade refers to the age of the most recent common ancestor of all of the species in the clade. The stem age of a clade refers to the time that the ancestral lineage of the clade diverged from its sister clade.
Next, the researcher returns and captures another sample of individuals. Some individuals in this second sample will have been marked during the initial visit and are now known as recaptures. [6] Other organisms captured during the second visit, will not have been captured during the first visit to the study area.
Haeckel in 1866 placed the group in the phylum Moneres (from μονήρης: simple) in the kingdom Protista and defines them as completely structureless and homogeneous organisms, consisting only of a piece of plasma. [10] He subdivided the phylum into two groups: [10] die Gymnomoneren (no envelope)