What do you call a beneficial trait that helps an organism to survive and reproduce?

Answer 1

An Adaptation.

It's actually a good definition.

There are other "-aptation" words, including "nonaptation," meaning a trait that doesn't affect an animal's survival, and "disaptation," meaning a trait that hinders the critter. Disaptations are usually aptations that were once beneficial and still exist in the species because they haven't been bred out yet through selective pressures.

Answer 2

a beneficial trait.

I think the book answer is probably "an adaptation," but that's a terrible definition of adaptation.