What's the most common type of mutation, and what impact does it have on natural selection?

The most common type of mutation is a deleterious mutation. Natural selection acts to remove this allele from the population.

Explanation:

If in your case there is abundant everything, then the answer is simple. Without anything in the way to stop Life, it will expand and grow throughout the universe. Therefore, your answer is the population will just keep on growing and growing, unless something prevents that.