25. The respiratory centers that control ventilation of the lungs in mammals are located in the
(A)brainstem.
(B)hypothalamus.
(C)cerebral cortex.
(D) bronchi.
(E) neck.

21. Which structure prevents blood flowing back into the atria during ventricular contractions? (A)atrioventricular valves (B)semilunar valves (C)sinoatrial node (D) carotid blood shunts (E) foramen ovale

22. Which of the following statements about RNA polymerase in bacteria is INCORRECT? (A)It binds the promoter region of a gene. (B)It is bound to a sigma factor during initiation of transcription. (C)It synthesizes RNA. (D) It catalyzes the addition of nucleotides to the 5′end of a growing RNA strand. (E) It dissociates from the DNA at the terminator.

23. Surgical removal of the pancreas would (A)increase the acidity of the small intestine. (B)prevent the production of chyme in the stomach. (C)eliminate the ability to store bile in the gallbladder. (D) block the secretion of bile. (E) All of these changes would be a result of pancreas removal.

24. What protein is involved in synthesizing messenger RNA in eukaryotes? (A)RNA polymerase I (B)RNA polymerase II (C)RNA polymerase III (D) sigma factor (E) both RNA polymerase I and II

26. The ascending portion of the loop of Henle is (A)permeable to water and impermeable to sodium. (B)permeable to water and permeable to sodium. (C)impermeable to water and permeable to sodium. (D) impermeable to water and impermeable to sodium. (E) the site of active transport of water.

27. MicroRNAs (miRNAs) (A)are long RNA molecules. (B)promotes post-translational modification of proteins. (C)are found only in animals. (D) are cut by an enzyme called transcriptase. (E) silence the expression of specific mRNAs. 

28. Which of these hormone-effect pairs is mismatched? (A)growth hormone-linear growth (B)glucagon-blood pressure (C)aldosterone-blood osmolality (D) thyroid hormone-metabolism (E) glucagon-glucose regulation

29. Alternation of generations means (A)One phase of the life cycle takes place on land and the other in water. (B)One phase of the life cycle is photosynthetic and the other is heterotrophic. (C)One phase of the life cycle is diploid and the other is haploid. (D) One phase of the life cycle is unicellular and the other is multicellular. (E) One phase of the life cycle is motile and the other is stationary.

30. The tracheae of adult terrestrial insects have been a factor in the great abundance of insects because they serve the same function in terms of the delivery of respiratory gases to the cells as do (A)the gills of aquatic insects. (B)the lungs of mammals. (C)the book lungs of spiders. (D) the closed circulatory system of cephalopods. (E) the Malpighian tubules of spiders.

31. Sister chromatids separate during (A)prophase of meiosis I. (B)metaphase of meiosis I. (C)metaphase of meiosis II. (D) prometaphase of meiosis I. (E) anaphase of meiosis II.