the galapagos mockingbird species mimus trifasciatus had an initial mean wing span of 7 cm. after a harsh winter, during which many birds died from starvation, the remaining mockingbirds had a mean wing span of 10 cm. if the wing span of their offspring is 8 cm, what are the values of the selection differential (s), heritability (h2), and difference in means (δz)? group of answer choices