Next > Muscular Strength and Endurance: Mastery Test
4
Select the correct answer.
What must skeletal muscles do to move?
A.
engage their fibers slowly
В.
twitch involuntarily
Oc.
separate from the bone
O D.
contract and relax
Reset
Next

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.