All 4 Uses

mutation
in
Starship Troopers
(Auto-generated)

You see, it's short on mutations; it does not enjoy Earth's high level of natural radiation.†
Chpt 11 *
With its evolutionary progress held down almost to zero by lack of radiation and a consequent most unhealthily low mutation rate, native life forms on Sanctuary just haven't had a decent chance to evolve and aren't fit to compete.†
Chpt 11
This chap told me that they could improve a little through mutation from other causes, from new blood added by immigration, and from natural selection among the gene patterns they already own — but that is all very minor compared with the evolutionary rate on Terra and on any usual planet.†
Chpt 11
Accepting, of course, the immediate dangers of radiation to themselves in order to provide a proper genetic heritage of mutation for the benefit of their descendants.†
Chpt 11

Definitions:

(1) (mutation)
a change in the genes that determine biological traits; or the result of the change
(2) (meaning too rare to warrant focus)