Answer
Mutations are the material on which evolution works and natural selection eliminates some and promotes others based on what best survives and reproduces.
Work Step by Step
Mutations create genetic variation, increasing it, but not all variants are equally well adapted to survive and reproduce. When natural selection acts, some variants/mutants either die or reproduce poorly, being eventually removed from the gene pool after first being reduced in frequency. This can be thought of as the disposal of those individuals, and, thus, of their genes, from future consideration by natural selection.
