Evolution is not continuous. It is a jerky and a discontinuous process. This is the punch line of

Variation in gene frequencies within populations can occur by chance rather than by natural selection. This is referred to as

Genetic drift operates in

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

Given below are two statements.
Statement $I$ - According to Darwin,the gradual,inheritable variations over a long period of time lead to speciation.
Statement $II$ - According to Hugo de Vries,mutations are the cause of variations.
In the light of above statements,select the correct option given below:

To be evolutionarily successful,a mutation must occur in the