68. Blood carbon dioxide levels determine the pH of other body fluids as well as blood, including the pH of cerebrospinal fluid. How does this enable the organism to control breathing?
(A) The brain alters the pH of the cerebrospinal fluid to force the animal to retain more or less carbon dioxide.
(B) The medulla is able to control the concentration of bicarbonate ions in the blood.
(C) The brain directly measures and monitors carbon dioxide and causes breathing changes accordingly.
(D) Stretch receptors in the lungs cause the medulla to speed up or slow breathing.
(E) The medulla, which is in contact with cerebrospinal fluid, monitors pH and uses this measure to control breathing

64. Beginning with the germination of a moss spore, what is the sequence of structures that develop after germination? 1. embryo 2. sporophyte 3. gametes 4. protonema 5. gametophore (A) 4 → 3 → 5 → 2 → 1 (B) 4 →1 → 3 → 5 → 2 (C) 4 → 5 → 2 → 1 → 3 (D) 4→ 5 → 3 → 1 → 2 (E) 4 → 5 → 1 → 2 → 3

65. Arrange the following structures, which can be found on male pine trees, from the largest structure to the smallest structure (or from most inclusive to least inclusive). 1. sporophyte 2. microsporangia 3. microspores 4. pollen cone 5. pollen nuclei (A) 1, 4, 3, 2, 5 (B) 1, 4, 2, 3, 5 (C) 1, 2, 3, 5, 4 (D) 4, 3, 2, 1, 5 (E) 1, 4, 2, 5, 3

66. How does the fass mutation in Arabidopsis result in a stubby plant rather than a normal elongated one? (A) Meristem identity genes produce defective transcription factors, resulting in a stubby shoot. (B) Juvenile nodes retain their juvenile status and elongated cells do not develop. (C) The cell's pattern of migration in the apical meristem is disrupted. (D) Lack of formation of the preprophase band results in random planes of cell division. (E) Cellulose microfibrils in the cell wall do not form, resulting in a shorter plant.

67. Mitochondrial DNA is primarily involved in coding for proteins needed for electron transport. Therefore in which body systems would you expect most mitochondrial gene mutations to be exhibited? (A) Circulation. (B) The skin and senses. (C) Nervous and muscular systems. (D) Excretory and respiratory systems. (E) The immune system and the blood.

69. How do ADH and RAAS work together in maintaining osmoregulatory homeostasis? (A) ADH monitors appropriate osmolarity by reabsorption of water, and RAAS maintains osmolarity by stimulating K+ reabsorption. (B) ADH monitors appropriate osmolarity by reabsorption of water, and RAAS maintains osmolarity by stimulating Cl－ reabsorption. (C) Only when they are together in the receptor sites of proximal tubule cells, will reabsorption of essential nutrients back into the blood take place. (D) ADH monitors appropriate osmolarity by reabsorption of water, and RAAS maintains osmolarity by stimulating Na+ reabsorption. (E) ADH and RAAS work antagonistically; ADH stimulates water reabsorption during dehydration and RAAS removes water when it is in excess in body fluids.

70. From earliest to latest, the overall sequence of early development proceeds as follows: (A) first cell division → synthesis of embryo's DNA begins → acrosomal reaction → cortical reaction. (B) first cell division → cortical reaction → acrosomal reaction → synthesis of embryo's DNA begins. (C) acrosomal reaction → cortical reaction → synthesis of embryo's DNA begins → first cell division. (D) cortical reaction → synthesis of embryo's DNA begins → acrosomal reaction → first cell division. (E) cortical reaction → acrosomal reaction → first cell division → synthesis of embryo's DNA begins.

71. Which of the following is the CORRECT sequence that occurs during the excitation and contraction of a muscle cell? 1. Calcium is released and binds to the troponin complex. 2. Tropomyosin shifts and unblocks the cross-bridge binding sites. 3. Transverse tubules depolarize the sarcoplasmic reticulum. 4. The thin filaments are ratcheted across the thick filaments by the heads of the myosin molecules using energy from ATP. 5. An action potential in a motor neuron causes the axon to release acetylcholine, which depolarizes the muscle cell membrane. (A) 2, 1, 3, 5, 4 (B) 2, 1, 3, 4, 5 (C) 5, 3, 2, 4, 1 (D) 5, 3, 1, 2, 4 (E) 5, 3, 2, 1, 4

72. If a Drosophila female has a homozygous mutation for a maternal effect gene, (A) only her male offspring will show the mutant phenotype. (B) her offspring will show the mutant phenotype only if they are also homozygous for the mutation. (C) all of her offspring will show the mutant phenotype, regardless of their genotype. (D) only her female offspring will show the mutant phenotype. (E) she will not develop past the early embryonic stage.

73. Which of the following poses the greatest potential threat to biodiversity? (A) replanting after a clear cut, a monoculture of Douglas fir trees on land that consisted of old growth Douglas fir, western cedar, and western hemlock. (B) trapping and relocating large predators, such as mountain lions, that pose a threat as they move into areas of relatively dense human populations. (C) importing an Asian insect into the United States to control a weed that competes with staple crops. (D) allowing previously used farmland go fallow and begin to fill in with weeds and then shrubs and saplings. (E) releasing sterilized rainbow trout to boost the sport fishing of a river system that contains native brook trout.

74. "Primary" succession is succession that (A) involves establishment of primary producers. (B) leads to establishment of a climax community dominated by primary producers. (C) occurs on newly exposed geologic substrates, not organic soil. (D) occurs where organic soils have been exposed but not destroyed by disturbance. (E) occurs after fire or agricultural abandonment.