Agroup that is limited to a common ancestor and all of its descendants is called

the father in the first generation probably had the recessive colorblind trait in his x chromosome. if he and his wife both had the colorblind trait, even if she had 1 recessive and 1 dominant, then that trait would be passed on to their kids.

(since you didn't attach the family tree this is just an assumption)

the correct answer is:

a population changes in response to a change in the environment.