53. The Morakot typhoon inflicted catastrophic damages on rivers and wiped out entire population of fishes in the river. This is an example of
(A) a density-dependent effect.
(B) the effects of abiotic factors.
(C) the interaction between density-dependent and abiotic factors.
(D) founder effect.
(E) dispersal effect.

49. Which of the following statements regarding balancing selection is FALSE? (A) The balancing selection maintains genetic diversity in a population. (B) The balancing selection can create a balanced polymorphism. (C) Homozygote advantage is usually favored by the balancing selection. (D) The balancing selection is a type of natural selection which does not always cause the elimination of weaker alleles. (E) The balancing selection can occur through negative frequency-dependent selection.

50. Isolated populations will lose a percentage of their original diversity over time, approximately at the rate of 1/(2N) per generation, where N= population size. After 20 generations, the original population of 500 will lose ___ of its original genetic variation. (A) 20% (B) 2% (C) 4% (D) 8% (E) 16%.

 51. Which of the following statements about umbrella species is correct? (A) Umbrella species are species whose habitat requirements are critical to a certain small area. (B) The Northern spotted owl (Strix occidentialis) is considered to be an important umbrella species. (C) The gopher tortoises (Gopherus polyphemus) is considered to be an important umbrella species. (D) Umbrella species must be attractive and more readily engendered support from the public for their conservation. (E) Formosan macaques are considered to be an important umbrella species in Taiwan.

52. In present populations of Taiwan Hwa-Mei (Leucodioptron taewanum) in Taiwan, genetic diversity has been (A) lost through mutation and restored by natural selection. (B) lost through stabilizing selection and restored by balancing selection. (C) lost through directional selection and restored by balancing selection. (D) lost through hybridization and restored by natural selection. (E) lost through artificial selection and restored by natural selection.

54. Which of the following mating systems does the Pheasant-tailed Jacana (Hydrophasianus chirurgus) exhibit in paddy fields in Tainan? (A) monogamy (B) polyandry (C) polygyny (D) promiscuity (E) none of the above

55. When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both redand white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result? (A) The gene involved is on the X chromosome. (B) The gene involved is on the Y chromosome. (C) The gene involved is on an autosome. (D) Other male-specific factors influence eye color in flies. (E) Other female-specific factors influence eye color in flies.

56. Sequencing an entire genome, such as that of Caenorhabditis elegans, a nematode, is most important because (A) it allows researchers to use the sequence to build a "better" nematode, resistant to disease. (B) it allows research on a group of organisms we do not usually care much about. (C) the nematode is a good animal model for trying out cures for viral illness. (D) a sequence that is found to have a particular function in the nematode is likely to have a closely related function in vertebrates. (E) a sequence that is found to have no introns in the nematode genome is likely to have acquired the introns from higher organisms.

57. Countercurrent exchange in the fish gill helps to maximize which of the following? (A) endocytosis (B) blood pressure (C) diffusion (D) active transport (E) osmosis

58. Sexual reproduction (A) allows animals to conserve resources and reproduce only during optimal conditions. (B) can produce diverse phenotypes that may enhance survival of a population in a changing environment. (C) yields more numerous offspring more rapidly than is possible with asexual reproduction. (D) enables males and females to remain isolated from each other while rapidly colonizing habitats. (E) guarantees that both parents will provide care for each offspring.

59. Members of two different species possess a similar-looking structure that they use in a similar fashion to perform the same function. Which information would best help distinguish between an explanation based on homology versus one based on convergent evolution? (A) The two species live at great distance from each other. (B) The two species share many proteins in common, and the nucleotide sequences that code for these proteins are almost identical. (C) The sizes of the structures in adult members of both species are similar in size. (D) Both species are well adapted to their particular environments. E) Both species reproduce sexually.