25 64 most of the dry mass of a plant is derived from

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Unformatted text preview: a plant is derived from (A) (B) (C) (D) (E) minerals from the soil carbon from the soil carbon from the atmosphere oxygen from the atmosphere oxygen from soil water 67. If the egg cell of a megagametophyte of a flowering plant has a marker gene designated as X and the sperm cell of a compatible pollen grain has a marker gene designated as Y, which of the following represents the endosperm that will result from fertilization in most flowering plants? (A) (B) (C) (D) (E) XX YY XY XXY YYX 65. Chlorophylls a and b are two pigments primarily responsible for the capture and processing of solar energy in the light reactions of photosynthesis. Which of the following best explains why having both chlorophyll a and b benefits a plant more than having one? (A) Chlorophylls a and b have slightly different absorption spectra; this expands the range of wavelengths of light that can be captured for photosynthesis. (B) Chlorophyll a is primarily involved in electron transfer; chlorophyll b is mainly involved in the capture of light energy. (C) Chlorophyll a captures all the solar energy; chlorophyll b serves to protect chlorophyll a from overexcitation. (D) Chlorophyll b captures all the solar energy; since chlorophyll a is a precursor to chlorophyll b, a pool of chlorophyll a must be maintained. (E) Chlorophyll a resides in the thylakoid membranes and captures light energy there; chlorophyll b is soluble in the chloroplast stroma and captures light energy there. 66. The Calvin cycle, the “dark reactions” or carbon fixation reactions of photosynthesis, cannot occur at night in a living plant. Which of the following best describes why this is true? (A) The stomata are incapable of opening at night, thus CO2 cannot enter the leaf. (B) The reactions of the Calvin cycle are dependent on light reactions for high-energy compounds. (C) Several enzymes necessary for Calvin cycle activity have been degraded during the day and must be replaced. (D) Light is required to transport the water necessary for the cycle. (E) Cooler temperatures at night slow enzyme activity and rates of substrate diffusion. 68. Ca2+ is important in skeletal muscle contraction because it (A) activates the myosin ATPase by binding to it (B) binds to troponin to remove a constant inhibition of cross-bridge attachment (C) prevents the formation of bonds between the myosin cross bridges and the actin filament (D) is required to detach the myosin head from the actin filament (E) causes muscle relaxation at intracellular concentrations of Ca2+ higher than 10−6M 69. Which of the following structures present in the embryos of higher plants develops into the primary root of the seedling? (A) (B) (C) (D) (E) Epicotyl Hypocotyl Cotyledon Radicle Endosperm 70. Which of the following statements about the motility of Paramecium is true? (A) (B) (C) (D) (E) Paramecium employs a pseudopod. Paramecium has no structures for motility. Paramecium uses a single flagellum. Paramecium uses a pair of flagella. Paramecium uses cilia. GO ON...
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