If we had a large population, say bacteria, of some billions of organisms, and among them they had 1000000 harmful mutations and one beneficial one what would be the result.

The 100000 with harmful mutations would die so we’d be left with a population of several billions of ‘fit’ bacteria less a few dead ‘unfit’ ones plus one with a beneficial mutation. That individual would probably survive and produce more offspring over successive generations than the rest and, like the effects of compound interest, its gene’s would soon dominate the gene pool. Of course at that rate you’d have at each generation the addition of a percent of so of harmfully mutated individuals and a new beneficially mutated one each round so over a million generations you’d have a population that looked nothing like the original as it had accumulated around one beneficial mutation per generation and remember that number of bacteria can live in a thimble sized body of water and will reproduce more than once per day. How many beneficial mutations does this equate to if we count all the organisms over the whole of the earth over 3.5 billion years?