38. Trace elements are those required by an organism in only minute quantities. Which of the following is a trace element that is needed by all forms of life?
(A) calcium
(B) iron
(C) iodine
(D) sodium
(E) potassium

34. Which of the following statements about circulatory systems is FALSE? (A) Arthropods and earthworms have open circulatory system. (B) The pulmonary circuit carries blood between the heart and gas exchange tissues in the lungs. (C) The systemic circuit carries blood between the heart and the rest of the body. (D) Salmon has a single circuit of blood flow and two heart chambers. (E) Mammals have two atria and two ventricles in their hearts.

35. In eukaryotic cells, 5S rRNA gene is transcribed by _____. (A) RNA polymerase I (B) RNA polymerase II (C) RNA polymerase III (D) RNA polymerase IV (E) RNA polymerase V

36. ________ is produced in the roots of plants. It promotes cell division and growth, and retards the aging of flowers and leaves? (A) Ethylene (B) Abscisic acid (C) Karrikins (D) Cytokinins (E) Gibberellins

37. Which of the following statements regarding cytoskeleton is true? (A) The subunit of microfilaments is tubulin. (B) The subunit of intermediate filaments can be dyneins. (C) The subunit of intermediate filaments can be keratin. (D) The subunit of intermediate filaments can be kinesins. (E) Microtubules are polymers of alpha and beta actin.

39. Which is a functional group that helps stabilize proteins by forming covalent cross-links within or between protein molecules? (A) amino group (B) carboxyl group (C) sulfhydryl group (D) carbonyl group (E) phosphate group

40. Which of the following is (are) the mechanism(s) of epigenetic varivations? (A) histone acetylation (B) single nucleotide substitution (C) DNA methylation (D) both A and C (E) all of A, B, and C

41. The process by which unrelated organisms with similar environment demands evolve superficially similar structures is (A) natural selection (B) homologous (C) convergent evolution (D) comparative anatomy (E) adaptation

42. On a daily basis, the amount of urine produced is approximately ___ of the amount of filtrate. (A) 80% - 90% (B) 50% - 60% (C) 30% - 40% (D) 10% - 20% (E) 1% - 2%

43. Which of the following is NOT a density-dependent regulation of population size? (A) competition (B) disease (C) predation (D) biotic potential (E) toxic waste

44. Breathing rate increases because of (A) insufficient oxygen in the blood (B) excess carbon dioxide in the blood (C) the accumulation of metabolites in the blood (D) both A and B (E) all of A, B, and C