- BS Media
- Published: 11, Jun, 2017 | Updated: June 11, 2017
- Splitting of the species into two or more species is called Speciation.
- Transformations of the old species into a new one in due course of time is known as transformation in time.
- Geographic isolation of demes of widely spread out population of a species over a period of a number of generations.
- Genetic differences are accumulated independently in each deme.
- Genetic divergence leading to the establishment of reproductive isolation.
Example: In the Australian continent, a bird “Acanthiza pusilla” is widely distributed. It slightly differ from the Tasmanian species - ‘A. Ewingi’. It is presumed that during pleistocene glaciation, when the sea level is lower, Acanthiza entered Tasmania. With the rise of sea level it became isolated and differentiated into A. ewingi.
iii) Sympatric speciation:
The chromosomal composition of P. virilis is regarded to be the ancestral type. The chromosomal complement of D. pseudo obscura and D. persimilis could tiave derived from D. virilis by a translocation between X chromosome and one of the autosomes. The chromosome compliment of D. melenogaster could be derived by two translocations between the two pairs of autosomes.