15. Which of the following is true of ammonia?
(A) It has low toxicity relative to urea.
(B) It can be stored as a precipitate.
(C) It is soluble in water.
(D) Only A and C are true.
(E) A, B, and C are true.

11. Pulse is a direct measure of (A) heart rate. (B) stroke volume. (C) breathing rate. (D) blood pressure. (E) cardiac output.

12. Which of the following blood components would interfere with the functioning of an open circulatory system but not a closed one? (A) red blood cells (B) antibodies (C) water (D) electrolytes (E) amino acids

13. HIV targets include all of the following except (A) cytotoxic T cells. (B) cells bearing CD4 and fusin. (C) brain cells. (D) macrophages. (E) helper T cells.

14. Both the eye and the respiratory tract are protected against infections by which of the following? (A) the mucous membranes that cover their surface (B) the secretion of complement proteins (C) the secretion of lysozyme onto their surface (D) interferons produced by immune cells (E) the release of slightly acidic secretions

複選題16. Unlike an earthworm's metanephridia, a mammalian nephron (A) forms urine by changing the composition of fluid inside the tubule. (B) is intimately associated with a capillary network. (C) functions in both osmoregulation and the excretion of nitrogenous wastes. (D) processes blood instead of coelomic fluid. (E) has a transport epithelium.

17. Short blood vessels connect two capillary beds lying in which of the following? (A) anterior pituitary and posterior pituitary. (B) hypothalamus and thalamus (C) anterior pituitary and adrenal gland. (D) posterior pituitary and thyroid gland (E) hypothalamus and anterior pituitary

18. Prolactin stimulates mammary gland growth and development in mammals and regulates salt and water balance in freshwater fish. Many scientists think that this wide range of functions indicates which of the following? (A) Prolactin is a nonspecific hormone. (B) Prolactin is an evolutionary conserved hormone. (C) Prolactin has a unique mechanism for eliciting its effects. (D) Prolactin interacts with many different receptor molecules. (E) Prolactin is derived from two separate sources.

19. Which of the following is not required for internal fertilization? (A) copulatory organ (B) internal development of the embryo (C) sperm receptacle (D) behavioral interaction (E) All of the above are necessary for internal fertilization.

20. There are five hormones regulating the human menstrual and ovarian cycles. Which of these structures secrete(s) these hormones? (A) hypothalamus (B) pancreas (C) ovaries (D) A and C only (E) A, B, and C

21. Which of the following statements is (are) true concerning the vitelline layer of the sea urchin egg? (A) It has receptor molecules that are specific for binding acrosomal proteins. (B) It releases calcium, which initiates the cortical reaction. (C) It is outside the fertilization membrane. (D) A and B are true. (E) A, B, and C are true.