Mutations are not beneficial; they're random. These mutations produce changes and are inherited . All organisms have tha same base pairs adenine guanine etc . You change only one percent of our functional DNA not exons, and you get a chimp and you change more and you get a rat.If you agree that mutations occur that can change an organism it should be reasonable that the changes would be huge over say 100,000,000 years leading to the biodiversity seen today