44. In mammals, the melanocytes ultimately arise from
(A) the endoderm.
(B)the mesoderm.
(C)the ectoderm.
(D)the notochord. (
(E) the neural tube.

40. Most of the carbon dioxide in the blood of humans is transported (A) as dissolved CO2 in plasma. (B)as bicarbonate ion in plasma. (C)attached to hemoglobin in red blood cells. (D)attached to hemoglobin in plasma. (E) as carbonic acid.

41. What is the correct rank order for relative toxicity (most to least) of the primary nitrogenous wastes used by different animals? (A) ammonia > urea > uric acid (B)uric acid > ammonia > urea (C)urea > uric acid > ammonia (D)ammonia > uric acid > urea (E) urea > ammonia > uric acid

42. Parathyroid hormone's main function is to (A) increase glucose mobilization during stress or fasting. (B)increase calcium by mobilizing the ion from bone. (C)increase sodium through reabsorption from kidney. (D)increase basal metabolic rate. (E) antogonized with thyroid hormone in various functions.

43. Fertilization of an ovum of human normally occurs in the (A) uterus. (B)ovary. (C)oviduct. (D)vagina (E) cervix.

45. To infect a cell, HIV must (A) kill cytotoxic T cells and bind CD4. (B)bind both CD8 and a cytokine co-receptor. (C)bind both CD8 and a class I MHC protein. (D)bind both CD4 and a cytokine co-receptor. (E) bind CD4 and kill macrophage.

46. In animals, the chemicals used to attract mates are called (A) hormones. (B)allomones. (C)pheromones. (D)allelopaths. (E) genetic byproducts.

47. If the number of individual is N, and the carrying capacity is K, and dN/dt as the rate of population growth. Base on the formula, dN/dt = rN(K-N)/K, the rate of population growth less than zero as (A) carrying capacity approaches zero. (B)the age-specific fertility rate approaches zero. (C)the per capita growth rate declines. (D)the population size approaches the carrying capacity. (E) the population size over the carrying capacity.

48. Competition among individuals of different species is called (A) resource competition. (B)basal competition. (C)interspecific competition. (D)intraspecific competition. (E) commensalism.

49. Community ecology is best defined as the study of (A) plant distributions in a given region. (B)mutual benefits between organisms at all scales in a region. (C)the relationship between abiotic and biotic factors. (D)global scale influences of major disturbances such as volcanos. (E) how groups of species interact in the same place at the same time

50. What is gross primary production? (A) The carbon fixed during photosynthesis. (B)The carbon fixed after cellular respiration is accounted for. (C)The mass increase of producers. (D)Photosynthetic production plus energy recycled by detritivores. (E) Total sun radio energy received by earth