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Unformatted text preview: Biology 172 Exam 4 2 1) The main source of water necessary for photosynthesis to occur in the leaves is: A. the soil via the xylem B. the soil via the phloem C. the atmosphere through the stomata D. the atmosphere through the plasmodesmata 2) Water potential ( ) in plants is produced by solute potential and pressure potential. Consider two plant cells A and B adjacent to each other. The solute potential ( S ) of cell A is 0.35 MPa, and its pressure potential ( P ) is +0.15 MPa. The solute potential ( S ) of cell B is 0.30 MPa, and its pressure potential ( P ) is +0.05 MPa. In which direction will net movement of water occur? A. Neither; cells A and B are in equilibrium with each other. B. from cell A to cell B C. from cell B to cell A 3) Which of the following is not evidence supporting the hypothesis that sugar translocation in phloem (phloem loading) is an active (energy-requiring) process? A. Sucrose occurs in higher concentrations in phloem companion cells than in the leaf cells where it is produced. B. Movement of water occurs from xylem to phloem and back again. C. Large pH differences exist between the interior and exterior of phloem companion cells. D. Strong charge differences exist between the interior and exterior of phloem companion cells. E. H +-ATPases are abundant in the plasma membranes of phloem companion cells. 4) What would happen if body temperature in mammals were controlled by a positive feedback system? A. More effectors would be needed to maintain the set point. B. Different integrators would be needed to maintain the set point. C. The body temperature would move increasingly away from the set point and result in death . D. The body temperature would be maintained much closer to the set point, reducing stress on the animal MORE QUESTIONS ON THE NEXT PAGE Biology 172 Exam 4 3 5) Earthworms in Michigan live in burrows in soil and maintain moisture on their skin, which serves as a surface for gas exchange. If you dropped one of these earthworms into the ocean, which of the following would most likely occur? A. The earthworm would be fine because it could breathe through its moist skin. B. The earthworm would lose water to the ocean by osmosis and would shrivel and die. C. The earthworm would gain too much water by osmosis from the ocean and would burst. D. The answer depends on the species of earthworm. 6) What problem would occur if the vasa recta blood vessels surrounding the loops of Henle were not functioning properly, so that water and salts removed from the pre- urine were not entering these blood vessels? A. Water could not enter or leave the proximal tubules. B. Pre-urine would become heavily concentrated with glucose, vitamins, electrolytes, amino acids, and urea....
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