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In [[biology]], a '''species''' is:
* a [[Typology|taxonomic]] rank (the basic rank of biological classification) or
* a unit at that rank (in which case the plural is "species". This is sometimes abbreviated: "spec." or "sp." singular, or "spp." plural).
There are many definitions of what kind of unit a species is (or should be). A common definition is that of a [[group]] of [[organisms]] capable of [[Mating|interbreeding]] and producing fertile offspring of both [[gender]]s, and separated from other such groups with which interbreeding does not ([[normally]]) happen. Other definitions may [[focus]] on similarity of [[DNA]] or [[morphology]]. Some species are further subdivided into subspecies, and here also there is no close agreement on the [[criteria]] to be used.
==Biologists' working definition==
A usable definition of the [[word]] "species" and reliable [[methods]] of identifying particular species is [[essential]] for stating and testing [[biological]] [[theories]] and for measuring biodiversity. [[Traditionally]], multiple examples of a proposed species must be [[studied]] for unifying characters before it can be regarded as a species. It is generally difficult to give precise taxonomic rankings to extinct species known only from [[fossils]].
Some [[biologists]] may see species as [[statistical]] [[phenomena]], as opposed to the [[traditional]] [[idea]], with a species seen as a class of [[organisms]]. In that case, a species is defined as a separately [[evolving]] lineage that forms a single gene pool. Although properties such as [[DNA]]-sequences and morphology are used to help separate closely-related lineages, this definition has fuzzy boundaries.[1] However, the exact definition of the term "species" is still controversial, particularly in [http://en.wikipedia.org/wiki/Prokaryotes prokaryotes],[2] and this is called the species problem.[3] Biologists have proposed a range of more [[precise]] definitions, but the definition used is a [[Practical|pragmatic]] [[choice]] that depends on the particularities of the species concerned.[http://en.wikipedia.org/wiki/Species]
[[Category: Biology]]
In [[biology]], a '''species''' is:
* a [[Typology|taxonomic]] rank (the basic rank of biological classification) or
* a unit at that rank (in which case the plural is "species". This is sometimes abbreviated: "spec." or "sp." singular, or "spp." plural).
There are many definitions of what kind of unit a species is (or should be). A common definition is that of a [[group]] of [[organisms]] capable of [[Mating|interbreeding]] and producing fertile offspring of both [[gender]]s, and separated from other such groups with which interbreeding does not ([[normally]]) happen. Other definitions may [[focus]] on similarity of [[DNA]] or [[morphology]]. Some species are further subdivided into subspecies, and here also there is no close agreement on the [[criteria]] to be used.
==Biologists' working definition==
A usable definition of the [[word]] "species" and reliable [[methods]] of identifying particular species is [[essential]] for stating and testing [[biological]] [[theories]] and for measuring biodiversity. [[Traditionally]], multiple examples of a proposed species must be [[studied]] for unifying characters before it can be regarded as a species. It is generally difficult to give precise taxonomic rankings to extinct species known only from [[fossils]].
Some [[biologists]] may see species as [[statistical]] [[phenomena]], as opposed to the [[traditional]] [[idea]], with a species seen as a class of [[organisms]]. In that case, a species is defined as a separately [[evolving]] lineage that forms a single gene pool. Although properties such as [[DNA]]-sequences and morphology are used to help separate closely-related lineages, this definition has fuzzy boundaries.[1] However, the exact definition of the term "species" is still controversial, particularly in [http://en.wikipedia.org/wiki/Prokaryotes prokaryotes],[2] and this is called the species problem.[3] Biologists have proposed a range of more [[precise]] definitions, but the definition used is a [[Practical|pragmatic]] [[choice]] that depends on the particularities of the species concerned.[http://en.wikipedia.org/wiki/Species]
[[Category: Biology]]
