What is the role of convection in plate tectonics?

a. convection causes the mantle to move, which moves the plates.

b. convection in the earths core causes the plates to move.

c. convection in the earths crust causes the sea floor to spread.

d. convection in the oceans pulls the sea floor.

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.