As you lift a heavier weight, what is happening? (select all that apply.) a. you increase the number of muscle fibers activated in each motor unit. b. you increase the number of motor units that are active in each activated muscle. c. you increase the frequency of action potentials in your motor neurons. d. you increase the diameter of muscle fibers activated in a motor unit.

Which of the following statements about c4 carbon fixation is not true? a c4 carbon fixation is an adaptation for plants exposed to high light intensityb. c4 carbon fixation occurs in more plants than c3 carbon fixation. c c4 carbon fixation is more common in areas of high temperatures than c3 carbon fixation. d. c4 carbon fixation occurs in the inner cells of a leaf rather than the entire leaf.

Plant species a has a diploid number of 12. plant species b has a diploid number of 16. a new species, c, arises as an allopolyploid from a and b. the diploid number for species c would probably be a) 12. b) 14. c) 16. d) 28. e) 56.

How are fossils used to date organisms?