What are the key concepts in the evolution theory of Darwin?

Explanation

Key concepts of Darwin's theory of evolution are as follows
(i) Over Production Living beings have an innate ability of producing own kind for the continuity of race. It has been observed that more individuals of each kind are produced than could possibly survive.
(ii) Struggle for Existence individuals multiply in geometric ratio, whereas space and food remain almost limited.
(iii) Variations Members of poopulation vary is size, form and other characteristics even though they look superficially similar, no two individuals are alike. These variations are gradual and those with adaptive value are passed on to next generation.
(iv) Survival of the Fittest and Natural Selection During struggle for existence only those individuals could survive which exhibit beneficial variations and adapt better to changing environment. This is known as natural selection.
(v) Origin of Species Natural Selection results in modification of traits whithin a lineage, which over a period of long time can bring about evolution of original species into new one.