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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.
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 bear with a salmon. Interspecific interactions such as predation are a key aspect of community ecology.. In ecology, a community is a group or association of populations of two or more different species occupying the same geographical area at the same time, also known as a biocoenosis, biotic community, biological community, ecological community, or life assemblage.
Cladistics (/ k l ə ˈ d ɪ s t ɪ k s / klə-DIST-iks; from Ancient Greek κλάδος kládos 'branch') [1] is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry.
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]
Later two further main ranks were introduced, making the sequence kingdom, phylum or division, class, order, family, genus and species. [4] In 1990, the rank of domain was introduced above kingdom. [5] Prefixes can be added so subkingdom (subregnum) and infrakingdom (also known as infraregnum) are the two ranks immediately below kingdom ...
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 ...
Informally, phyla can be thought of as groupings of organisms based on general specialization of body plan. [8] At its most basic, a phylum can be defined in two ways: as a group of organisms with a certain degree of morphological or developmental similarity (the phenetic definition), or a group of organisms with a certain degree of ...