I must disagree. Random mutations do not explain the steady progress of evolutionary changes. Changes occur, and these can be called mutations, but the mechanism by which a whole species goes from living on land to living in the sea is not explained by random mutation. Nor by natural selection dealing with the random mutations that do occur. Further, similar species have evolved in lands isolated from one another, such as Australia. There appears to be some inate quality that causes life to evolve and make use of the environment in various ways.
Yeah. It's inheritance, with variation, and natural selection.