23. The cell-mediated immunity that destroys virally infected cells involves _____. 

(A) cytotoxic T cells
(B) natural killer cells
(C) helper T cells
(D) macrophages
(E) B cells 

19. An inhibitory postsynaptic potential (IPSP) occurs in a membrane made more permeable to _____. (A) potassium ions (B) sodium ions (C) calcium ions (D) ATP (E) all neurotransmitter molecules

20. From earliest to latest, the overall sequence of early development proceeds in which of the following sequences? (A) gastrulation → organogenesis → cleavage (B) ovulation → gastrulation → fertilization (C) cleavage → gastrulation → organogenesis (D) gastrulation → blastulation → neurulation (E) preformation → morphogenesis → neurulation

21. In humans, the follicular cells that remain behind in the ovary following ovulation become _____. (A) the ovarian endometrium that is shed at the time of the menses (B) a steroid-hormone synthesizing structure called the corpus luteum (C) the thickened portion of the uterine wall (D) swept into the fallopian tube (E) the placenta, which secretes cervical mucus

22. Oxytocin and antidiuretic hormone are synthesized in the _____. (A) hypothalamus (B) adenohypophysis (C) anterior pituitary (D) adrenal cortex (E) posterior pituitary

24. The Bohr shift on the oxygen-hemoglobin dissociation curve is produced by changes in _____. (A) the partial pressure of oxygen (B) the partial pressure of carbon monoxide (C) hemoglobin concentration (D) temperature (E) pH

25. Hypoglycemia, or low levels of glucose in the blood of a healthy human, is "corrected" by a(n) _____. (A) increase in the secretion of insulin (B) increase in the secretion of glucagon (C) increase in the secretion of both insulin and glucagon (D) decrease in the secretion of both insulin and glucagon (E) increase in the secretion of thyroid hormones

26. Standard metabolic rate (SMR) and basal metabolic rate (BMR) are _____. (A) used differently: SMR is measured during exercise, whereas BMR is measured at rest (B) used to compare metabolic rate between hibernating and nonhibernating states (C) both measured across a wide range of temperatures for a given species (D) both standard measurements of fat metabolism in mammals (E) both measured in animals in a resting and fasting state

27. The transduction pathway that activates systemic acquired resistance in plants is initially signaled by _____. (A) antisense RNA (B) Pfr phytochrome (C) salicylic acid (D) abscisic acid (E) red, but not far-red, light

28. The asexual production of seeds from a diploid cell, allow hybrid plants to pass on their desirable genomes intact to their offspring is called _____. (A) apomixis (B) dioecious (C) etiolation (D) phyllotaxy (E) statoliths

29. A flowering plant with a deleterious mutation in microsporogenesis would most likely _____. (A) fail to produce sepals (B) fail to produce petals (C) fail to produce anthers (D) fail to produce pollen (E) fail to produce ovules