Mutation does not always affect the evolution of a species because

not all mutations are inherited

not all mutations are beneficial

not all mutations cause visible change

not all mutations affect an entire species

not all mutations cause visible change

Not all mutations are inherited

Explanation:

Each cell of living beings has DNA and therefore, mutations can occur in both somatic and germ cells. However, the mutations that have occurred in somatic cells would not be passed to the next generations. The only mutations that occur in germ cells are inherited to the next generations.

Evolution requires inheritances of variations to give rise to a new species. Since the mutations in somatic cells are not inherited, they will not cause any evolution. The mutations of the germ cells would serve as raw material for evolution. Hence, mutations do not always cause the evolution of species as they may occur in both somatic and germ cells.