What's the result of a normal palpebral reflex? a. a light tap on the medial canthus causes increased tear production. b. a light tap on the lateral canthus of the eye produces vasoconstriction. c. a light tap on the medial canthus of the eye produces a blink of the eyelid. d. a light tap on the lateral canthus of the eye causes the eyeball to retract.

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.