50. Which of the following is not a component of an insect's defense against infection?
(A) phenoloxidase activation, leading to the formation of large deposits around parasites
(B) production of antimicrobial peptides
(C) activation of natural killer cells
(D) a protective exoskeleton
(E) phagocytosis by hemocytes

46. Which of the following is the best explanation for the inability of an animal cell to reduce the concentration in its cytosol compared with the extracellular fluid? (A) low oxygen concentration around the cell (B) loss of transcription factors (C) low levels of protein kinase in the cell (D) blockage of the synaptic signal (E) insufficient ATP levels in the cytoplasm

47. All of the following represent adaptations by terrestrial animals to drying conditions except (A) salt glands. (B) increased thirst. (C) efficient kidneys. (D) anhydrobiosis. (E) impervious surfaces.

Use the data in Table.I to answer question 48.The data were obtained from a study of the length of tirne spent in each phase of the cell cycle by cells of three eukaryotic organisms designated beta, delta, and gamma. 48. The best conclusion concerning delta is that the cells (A) contain only one chromosome that is very short. (B) contain no DNA. (C) contain no RNA. (D) divide in the G₁ phase. (E) are actually in the G0 phase.

49. Which of the following is a characteristic of the early stages of local inflammation? (A) attack by cytotoxic T cells (B) release of histamine (C) fever (D) antibody- and complement-mediated lysis of microbes (E) arteriole constriction

51. sexual reproduction and sexual reproduction are different in that (A) individuals reproducing asexually transmit 100% of their genes to their progeny, whereas individuals reproducing sexually only transmit 50%. (B) asexual reproduction produces offspring that are genetically identical to the parents, whereas sexual reproduction gives rise to genetically distinct offspring. (C) asexual reproduction involves a single parent, whereas sexual reproduction involves two. (D) asexual reproduction only requires mitosis, whereas exual reproduction always involves meiosis. (E) all of the above

52. Referring to a plant sexual life cycle, which of the following terms describes the process that leads directly to the formation of gametes? (A) sporophyte meiosis (B) gametophyte mitosis (C) gametophyte meiosis (D) sporophyte mitosis (E) alternation of generations

53. The F1 offspring of Mendel's classic pea cross always looked like one of the two parental varieties because (A) one allele was completely dominant over another. (B) each allele affected phenotypic expression. (C) the traits blended together during fertilization. (D) no genes interacted to produce the parental phenotype. (E) different genes interacted to produce the parental phenotype.

54. Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. This suggests (A) that the parents were true-breeding for contrasting traits. (B) incomplete dominance. (C) that a blending of traits has occurred. (D) that the parents were both heterozygous. (E) that each offspring has the same alleles.

55. New combinations of linked genes are due to which of the following? (A) nondisjunction (B) crossing over (C) independent assortment (D) mixing of sperm and egg (E) both A and C

56. Which of the following statements is (are) true? (A) The closer two genes are on a chromosome, the higher the probability that a crossover will occur between them. (B) The observed frequency of recombination of two genes that are far apart from each other has a maximum value of 50%. (C) Two of the traits that Mendel studied-seed color and flower color-are linked on the same chromosome. (D) Only B and C are correct. (E) A, B, and C are correct.