Each tissue and organ in the body has a function, and its metabolism is adapted to its function. For example, one tissue may synthesize fatty acids that are stored and oxidized by another tissue. Classify each phrase as describing the liver, adipose tissue, muscle tissue, the brain, or blood.

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.