Species
A species, according to the classification system used by biologists, is a group of living organisms having sufficient genetic similarity to be able to produce fertile offspring.[1]
For example, a tiger and a clam are classified as different species, because they cannot produce offspring. A German Shepherd and a Beagle, although different breeds, are classified as being the same species because they can produce fertile offspring.
However, the definition of "species" has changed over time and is sometimes problematic. For example, there are cases where two species are not capable of interbreeding, but each is capable of interbreeding with a third species.[2] Additionally, a "species" is sometimes defined in such a way that groups of creatures that do not naturally interbreed (perhaps because of geological isolation) are classified as separate species despite the fact that they can interbreed.[2] Furthermore, many extinct species known only from fossils have been given species names, despite the impossibility of determining their capability of interbreeding.
The origin of species
Linnaeus originally intended "species" to refer to the biblical creation "kinds", but the modern definitions of species do not match the biblical kinds. Nevertheless, many Christians and many evolutionists believe that the idea of new species developing is inconsistent with the Bible. However, creationary scientists accept that speciation has been observed, although they deny that speciation can lead to the development of completely new features as predicted by evolutionists.
Charles Darwin wrote The Origin of Species 167 years ago, hoping to account for the diversity of plant and animal life with an entirely naturalistic explanation (see Theory of evolution).
Ring Species
This is a phenomenon which occurs when a contiguous lineage ancestors co-exist at the same time. Unlike most species whose direct ancestral species are now extinct, the ancestral species of a ring species still survive. The existence of ring species make it more difficult to define what a species is. For example, A can breed with B can breed with C can breed with D... however D cannot breed with A. The most prominent example of a ring species is the Larus Gull which resides in the north Atlantic. Neighboring species interbreed counter-clockwise around the arctic, however this ability to interbreed terminates near Britain with the Herring Gull and Lesser Black-Backed Gull.[3]
Note
- â A group of organisms belong to the same biological species if they are capable of producing fertile offspring. Holgrem Lab, Northwestern University, Illinois
- â 2.0 2.1 Speciation (SparkNotes)
- â Harrison, Peter (1988): Seabirds (2nd ed.). Christopher Helm, London ISBN 0-7470-1410-8