41) The sun shining on a tidal pool during a hot day heats the water. As some water evaporates,
the pool becomes saltier, causing
A) a decrease in its carbon dioxide content.
B) a decrease in its oxygen content.
C) an increase in its ability to sustain aerobic organisms.
D) a decrease in the water’s density.
E) a decrease in the movement of the water molecules.
42) Sponges, cnidarians, and flatworms lack a specialized gas-exchange surface because
A) they are too large for a circulatory system to operate well.
B) they live without the need for oxygen.
C) they do not produce carbon dioxide.
D) countercurrent exchange mechanisms cannot function well in their living conditions.
E) nearly all of their cells are in direct contact with the external environment.
43) What happens to pH and breathing rate during exercise?
A) pH decreases, which causes breathing rate to increase.
B) pH decreases, which causes breathing rate to decrease.
C) pH increases, which causes breathing rate to increase.
D) pH increases, which causes breathing rate to decrease.
44) The amount of air inhaled and exhaled in a normal breath is called
A) residual volume.
B) vital capacity.
C) tidal volume.
D) countercurrent exchange.