What is the variation of traits among the members of a species called?

When Darwin spoke of the struggle for existence and survival of the fittest in nature,he was convinced that

Given below are the two statements.
Statement $I$: Directional isolation favours the intermediate forms and eliminates both phenotypic extremes.
Statement $II$: In directional isolation,more individuals acquire a value other than the mean character value.
In the light of the above statements,choose the correct answer from the options given below:

Select the correct statement from the given options.

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:

Which of the following can be used as an illustration to demonstrate the process of evolution in animals?