24. The postsynaptic membrane of a nerve may be stimulated by certain neurotransmitters to permit the influx of negative chloride ions into the cell. This process will result in
(A) the membrane becoming more positive.
(B) membrane depolarization.
(C) the production of an EPSP.
(D) the production of an IPSP.
(E) an action potential.

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.

22. Which mathematical situation has a parallel in embryonic limb development? (A) plotting a graph of a linear growth curve (B) using X, Y, and Z coordinates to plot a graph (C) plotting a graph of an exponential growth curve (D) using parallel lines to construct a parallelogram (E) E=MC²

23. Integration of simple responses to certain stimuli, such as the patellar reflex, is accomplished by which of the following? (A) medulla (B) hypothalamus (C) corpus callosum (D) cerebellum (E) spinal cord

25. The pathway leading to the perception of sound begins with the (A) hair cells of the organ of Corti, which rests on the tectorial membrane, coming in contact with the basilar membrane. (B) hair cells of the organ of Corti, which rests on the tympanic membrane, coming in contact with the tectorial membrane. (C) hair cells of the organ of Corti, which rests on the basilar membrane, coming in contact with the tectorial membrane. (D) hair cells on the tympanic membrane that stimulate the tectorial membrane neurons leading to the auditory section of the brain. (E) hair cells of the organ of Corti coming in contact with the tectorial membrane as a result of fluid waves in the cochlea causing vibrations in the round window.

26. What is the structure diagrammed in Figure 1? (A) an ommatidium (B) a neuromast (C) a statocyst (D) a taste bud (E) an olfactory bulb

27. Coral reefs can be found on the southern east coast of the United States but not at similar latitudes on the southern west coast. Differences in which of the following most likely account for this? (A) ocean currents (B) precipitation (C) sunlight (D) day length (E) salinity

28. Polar regions are cooler than the equator because (A) the poles are permanently tilted away from the sun. (B) there is more ice at the poles. (C) the poles have a thicker atmosphere. (D) sunlight strikes the poles at an oblique angle. (E) the poles are farther from the sun.

29. Reconciliation behavior is likely to follow (A) imprinting by young animals on a member of the wrong species. (B) conflict behavior between members of a permanent social group. (C) mating behavior between a male and a female. (D) agonistic behavior between territorial males. (E) ritualized behavior.

30. In the 14th century, _____ was responsible for the death of more than one-third of the entire European population of humans. (A) pneumonia (B) bubonic plague (C) AIDS (D) influenza (E) tuberculosis