SPECIES CONCEPT -

• According to Davis and Heywood species define as assemblage of individuals with morphological features in common and separable from other such assemblage by correlated morphological discontinuities in a number of features.
• Lumpers tend to combine populations into single species or groups.
• Splitters tend to separate the same populations into different species or groups.

BIOLOGICAL SPECIES CONCEPT -

• A species is a sexually interbreeding or potentially interbreeding group of individuals separated from other species by reproductive isolation that is by absence of genetic exchange.

SIBLING SPECIES CONCEPT -

• When the two species are morphologically almost identical but do not interbreed. e.g., Drosophila pseudoobscura and Drosophila persimilis are two species, do not cross-fertilize.

POLYTYPIC SPECIES CONCEPT -

• Morphologically and geographically separated species into a single species on the basis of their successful interbreeding is called polytypic species. e.g., North American sparrows - Passarella melodia.

EVOLUTIONARYCHRONO SPECIES CONCEPT -

• According to George Gaylord Simpson (1961) A species as a group of organism that is derived from its ancestor by a process of slow, steady evolutionary change and is not regarded as members of the same species as its ancestor.