Why is the term global warming often used when referring to climate change?

a) every location on earth is hotter every year than the year before.

b) the sea temperatures have increased by 20 degrees.

c) overall, the average surface temperature of the earth is increasing.

d) none of the above are true.

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.