47. Which of the following combination is correct?
(A) Porifera – coelomate, branch radial.
(B) Nematoda – earthworm, pseudocoelomate.
(C) Platyhelminthes – flatworms, pesudocoelomate.
(D) Echinodermata – branch bilateria, diploblastic.
(E) Cnidaria – radial symmetry, diploblastic.

43. Genetic variation is the result of all but (A) the role of environment in controlling genetic expression. (B) alteration in chromosome structure of number. (C) gene mutation. (D) independent assortment. (E) genetic recombination.

44. Consider a field plot containing 200 kg of plant material. How many kg of carnivore production can be supported? (A) 200 (B) 100 (C) 50 (D) 20 (E) 2

45. The most common pattern of dispersion in nature is (A) random. (B) uniform. (C) indeterminate. (D) dispersive. (E) clumped.

46. Which of the following statements about movement corridors is true? (A) A movement corridor connects otherwise isolated patches of quality habitat for a species. (B) Corridors can be constructed only by humans. (C) Riparian habitats frequently serve as effective corridors. (D) A and C are true. (E) A, B, and C are true.

48. A person suffering from AIDS would be unlikely to suffer from which of the following diseases? (A) Rheumatoid arthritis (B) Hepatitis (C) Tuberculosis (D) Influenza (E) Cancer

49. The vascular system of a three-year-old dicot stem consists of (A) 3 rings of xylem and 3 of phloem. (B) 2 rings of xylem and 2 of phloem. (C) 3 rings of xylem and 1 of phloem. (D) 1 rings of xylem and 3 of phloem. (E) 2 rings of xylem and 3 of phloem.

50. Within the female gametophyte, three mitotic divisions of the megaspore produce (A) the triple fushion nucleus and two synergids. (B) three pollen grains and three antipodal cells. (C) two antipodals and two eggs. (D) three antipodal cells,two polar nuclei, one egg, and two synergids. (E) a tube nucleus, a generative cell, an egg, and a sperm.

51. A pathogenic fungus invades a plant. Which of the following does the plant produce in response to the attack? (A) antibiotics (B) antisense RNA (C) phytochrome (D) phytoalexins (E) statoliths

52. Which of the following is correctly paired? (A) forebrain – diencephalons (B) midbrain – cerebellum (C) spinal cord – brainstem (D) both A and B are correct (E) both B and C are correct

53. Which of the following statements is false? (A) Estuaries support many semiaquatic species. (B) Many lakes in temperate regions are characterized by seasonal thermal stratification. (C) The distribution of photosynthetic organisms is limited by the quality and intensity of light in marine ecosystems. (D) Estuaries usually contain no or few producers. (E) Many aquatic biomes exhibit pronounced vertical stratification of chemical variables.