48. What mechanism leads to changes in allele frequencies due to random chance?
(A) Genetic drift
(B) Natural selection
(C) Sexual selection
(D) Neutral variation
(E) inbreeding

44. Vaccinations are effective in combating future infections because they induce the production of (A) helper T cells. (B) neutrophils. (C) prostaglandins. (D) mutations in the host genome. (E) memory cells.

45. All of the following are components of nonspecific immunity EXCEPT (A) skin. (B) phagocytes. (C)complement. (D) lysozyme. (E) B cells.

46. Which of the following is true of T cells and B cells? (A) They are effector cells against specific pathogens. (B) They are produced from stem cells of the bone marrow. (C) They can help attack and destroy invading pathogens. (D) They typically have a short life span. (E) All of these statements are true.

47. In the Hardy-Weinberg equation , the genotype frequency of heterozygotes is represented by (A) p2 (B) 2pq (C) q2 (D)p2+q2 (E) p2 + 2pq

49. A major disadvantage of using DNA or RNA sequences to identify species is that (A) it can only be used for sexually reproducing organisms. (B) it cannot be used for extinct species. (C) there are no rules for determining the number of sequence differences needed for a new species. (D) if can be misleading because many species exhibit large variation in phenotype. (E) it is expensive to sequence genomic DNA

50. Adaptive radiation is likely to have led to which of the following? (A) The divergence of a single pea aphid population into two distinct species. (B) The evolution of the horse via changes in climate and food supply. (C) The long period of equilibrium in a bat species in the Mariana Islands. (D) The 1,000 species of Drosophila found dispersed throughout the Hawaiian Islands. (E) A population of mountain goats are split because of the formation of a glacier.

1.For the reaction of sodium bromide with chlorine gas to form sodium chloride and bromine, the appropriate half-reactions are (ox = oxidation and re = reduction): (A) (B) (C)(D)(E)

2. The following reactions:  are examples of (A) acid-base reactions. (B) unbalanced reactions. (C) precipitation, acid-base, and redox reactions, respectively. (D) redox, acid-base, and precipitation reactions, respectively. (E) precipitation, redox, and acid-base reactions, respectively.

3.What volume of 18.0 M sulfuric acid must be used to prepare 15.5 L of 0.195 M H2SO4 ? (A) 168 mL (B) 0.336 L (C) 92.3 mL (D) 226 mL (E) none of these

4. Air has an average molar mass of 29.0 g/ mol. The density of air at 1.00 atm and 30°C is (A) 29.0g/L (B) 40.0g/mL (C) 1.17g/L (D) 1.29g/L (E) 12g/L