10. Which function associated with muscle would be most directly affected by low levels of calcium?
(A) The muscle fiber resting membrane potential.
(B) Muscle contraction.
(C) The initiation of an action potential.
(D) ATP hydrolysis.
(E) Muscle fatigue.

6. The acidity of the stomach contents triggers the small intestine to secrete a hormone known as (A) histones. (B) secretin. (C) TSH. (D) pepsin. (E) cholecystokinin, or CCK.

7. In which blood vessel is glucose concentration likely to vary the most? (A) coronary arteries. (B) abdominal artery. (C) hepatic vein, which drains the liver. (D) hepatic portal vessel. (E) pulmonary veins.

8. Which of the following is an example of countercurrent exchange? (A) The flow of water across the gills of a fish and that of blood within those gills. (B) The flow of air within the primary bronchi of a human and that of blood within the pulmonary veins. (C) The flow of blood in the dorsal vessel of an insect and that of air within its tracheae. (D) The flow of fluid out of the arterial end of a capillary and that of fluid back into the venous end of the same capillary. (E) The flow of water across the skin of a frog and that of blood within the ventricle of its heart. 

 9. What advantage does internal fertilization have compared with external fertilization? (A) Usually a smaller number of genes are present, which promotes genetic stability. (B) Usually many offspring are produced, ensuring survival of the species. (C) The time and energy devoted to reproduction is decreased. (D) The increased survival rate results in rapid population increases. (E) The smaller number of offspring often receive a greater amount of parental protection.

11. Phylogenetic trees are best described as (A) true and inerrant statements about evolutionary relationships. (B) the most accurate representations possible of genetic relationships among taxa. (C) theories of evolution. (D) hypothetical portrayals of evolutionary relationships. (E) the closest things to absolute certainty that modern systematics can produce.

12. Estimates of the number of species present in a community (A) are not affected by the sampling effort devoted to estimation. (B) usually require only limited effort by ecologists. (C) can usually be made more easily by sampling only a single indicator taxon. (D) are all that is necessary to calculate species diversity. (E) must, to be useful, be based on standardized sampling techniques.

13. A major perturbation of the carbon cycle by human activity is associated with (A) release of carbon from carbonate rocks. (B) release of carbon from fossil fuel deposits. (C) removal of carbon from the atmosphere in the industrial production of fertilizers. (D) accelerated removal of carbon from the atmosphere by forests. (E) respiratory production of CO2 by the large human population.

14. Which statement about changing ecosystem properties during succession is FALSE? (A) Biomass increases. (B) Soil depths decrease. (C) Primary production increases. (D) Community respiration increases. (E) Stream spiraling lengths decrease.

15. The nuclear genomes of eukaryotes are composed of different categories of sequences. Repetitive sequences are one type of the categories. Which of the following is an example of highly repetitive sequences? (A) Histone gene cluster . (B) Ribosomal RNA genes. (C) Homologous genes. (D) Alu elements. (E) Multigene families.

16. If the genes of a cell's spliceosomes were mutated so the spliceosomes no longer action normally. Which of the following would occur? (A) A functional protein would be produced. (B) Transcription would stop. (C) A primary transcript would not be produced. (D) Translation would stop. (E) Intron(s) would stay in the mature mRNA.