Evolution is the sequence of gradual changes which take place in the primitive organisms over millions of years and new species are produced. Since, the evolution is of the living organisms, so it is called ‘Organic Evolution’. Darwin’s theory of Evolution: Charles Robert Darwin gave the theory of evolution in his famous book, ‘The Origin of Species’. The theory of evolution proposed by Darwin is known as ‘The Theory of Natural Selection’. It is also called ‘Darwinism’.
According to Darwin’s theory of evolution:
(a) There is natural variation within any population and some individuals have more favourable variations than others.
(b) Population remains fairly constant even though all species produce a large number of off springs.
(c) This is due to ‘competition’ or struggle for existence between same and different species.
(d) The struggle for survival within population eliminates the unfit individuals and those with ‘favourable variations’ survive and pass on these variations to their progeny to continue. This is called natural selection.
(e) The favourable variations are accumulated over a long time period leading to the origin of a new species.