Analogous structures are a result of

Darwin,in his 'Natural Selection Theory',did not believe in any role of which one of the following in organic evolution?

According to Neo-Darwinism,which of the following is responsible for evolution?

Select the correct statement from the given options.

Given below are two statements regarding evolution.
$Statement-I$: Isolation is the separation of a population of a particular species into smaller units, which prevents interbreeding between them.
$Statement-II$: Due to isolating mechanisms, divergence and speciation do not occur.
In the light of the above statements, choose the most appropriate answer from the options given below.

According to Darwin,organic evolution is due to: