Which of the following statements are TRUE? 1. Coenzymes are molecules that bind to an enzyme, changing its shape to help the enzyme receive the substrate thus increasing the rate of the reaction.

2. Inhibitors are molecules that bind to an enzyme either changing its shape or blocking the active site thus decreasing the rate of the reaction.

3. Both the above statements.

4. Neither the above statements.

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.