The Biological Species Concept is the most used of the species concepts to explain the term species. Is this the most viable concept?
Introduction:
The definition of a species is defined using the Biological Species Concept, which states that groups of organisms are divided in populations and in these populations, the organisms can only breed with each other to produce fertile offspring (Campbell 2015). The formation of new species depends on reproductive isolation. There are factors which can block gene flow and between two species. For example, a tree cannot mate with a dog. These factors/barriers are grouped into prezygotic barriers and postzygotic barriers. Prezygotic barrier stops fertilization from occurring. One way in which this
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Two species of oak tree are different sizes and can tolerate two temperature conditions but they can still interbreed. This demonstrates that the two different trees where in different locations, under different conditions. When they come into contact, they could still interbreed because they are the same species of oak tree and where just adapted to different conditions. According to Van Valen (1976:235) he states that ‘A species is a lineage (or closely related linages) which occupies an adaptive zone minimally different from that of any other lineage in its range and which evolves separately from all other lineages outside its range’. Val Valen (1976) did not concentrate as much on the reproductive element and maintained that species are separated ecologically rather than reproductively. There are different levels of ecological differentiation, in polymorphic groups there are some animals which exhibit ecological differentiation. (Van Valen 1976) Ecological differences are important in a species but varies in different species. In comparison to the biological species concept the ecological species concept can be applied to both sexual and asexual organisms whereas in the biological species concept it cannot be applied to asexual species. (Campbell