Some factories have started using large tanks of bacteria to remove carbon dioxide from the atmosphere. As more factories start to do this, the amount of carbon dioxide in the atmosphere could decrease over time. If this happens, and if energy coming from the sun and the amount of carbon dioxide being put into the atmosphere otherwise stay the same, what would happen to the total amount of energy in the Earth system and to global average temperature

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.