Variations caused by mutation,as proposed by Hugo de Vries,are

The frequency of a character in a population is found to be increasing when:

How did Darwin explain the origin of species?

If there were no evolution,then .....

Arrange the events of Darwinism in the correct sequence.
$I -$ Natural selection
$II -$ Variations and their inheritance
$III -$ Survival of the fittest
$IV -$ Struggle for existence

What is a gene pool?