56. The enzyme that HIV uses to copy its RNA into DNA is__?
(A) Reverse transcriptase；
(B) RNA polymerase；
(C) RNA integrase；
(D) DNA polymerase.

52. Darwin concluded from his observations of nature and readings that__? (A) population growth is unlimited, leading to the large numbers of organisms；(B) individuals compete with one another for limited resources and only the fittest survive；(C) an individual's likelihood of survival and reproduction are mostly due to chance and changes in the environment；(D) individuals compete with one another for limited resources and only the fittest reproduce.

53. Natural selection acts on__? (A) genotypes；(B) populations；(C) individuals；(D) communities.

54. If similarities between two structures in different organisms reflect independent evolution, these structures are__? (A) heterologous；(B) homeotic；(C) homologous；(D) analogous.

55. The observation that most aquatic vertebrates (e.g. fish, penguins, and whales) have streamlined bodies and fins or flippers for steering are a result of__? (A) analogous selection；(B) convergent evolution；(C) sexual selection；(D) vestigial selection.

57. A vaccine against the influenza virus would result in production of antibodies against which of the following? (A) proteins in the envelope；(B) lipids in the envelope；(C) viral DNA；(D) viral RNA.

58. Viruses always lack which of the following? (A)an envelope；(B) organelles；(C) genetic material；(D) a protein coat.

59. A microbiologist Gram stains a bacterium and finds the bacterium to be pink to red in color, this identifies the__? (A) species of bacterium；(B) bacterium as a bacterium that causes human disease；(C) bacterium as gram-negative；(D) bacterium as gram-positive.

60. Escherichia coli and Salmonella can live in our intestines in the presence or absence of oxygen. They are considered which of the following? (A) facultative anaerobes；(B) autotrophs；(C) aerobic；(D) obligate anaerobes.

61. A gaseous hormone produced by plants that helps control fruit ripening is__? (A) dextrose；(B) carbon dioxide；(C) chlorophyll；(D) ethylene.

62. If a plant exhibits determinate growth, the plant__? (A) produces auxiliary roots to help stabilize the plant；(B) produces seeds only at one time during its life；(C) continues to grow until the environment determines that it cannot；(D) stops growing when the plant reaches its mature size.