"Reward" is subjective but I don't know how else to say it. A negative trait dies out. That could be construed as a "punishment" but evolution does not "punish" either. An organism which does not change at all in response to a change in conditions may be at a reproductive disadvantage to those organisms which do change. Or not.
It is difficult to avoid anthropomorphic terminology in evolutionary discussions but we must make an effort because the creationists will jump on any such loose end as "proof" for their fairy tales.
It is difficult to avoid anthropomorphic terminology in evolutionary discussions but we must make an effort because the creationists will jump on any such loose end as "proof" for their fairy tales.