Countercurrent exchange in the gills of fish is an adaptation that accomplishes which of the following?
a. It limits the amount of blood going to the gills.
b. It decreases the thermal gradient between water and blood.
c. It improves the ability of blood to dissolve oxygen.
d. It maximizes oxygen transfer from water to the blood.
e. It maximizes heat retention in the fish.
Ans: d. It maximizes oxygen transfer from water to the blood.
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The respiratory systems of fish and birds are similar in that both______________.
A. utilize air sacs. B. have similar partial pressures of oxygen in the environmental medium. C. have unidirectional flow of the environmental medium over the gas exchange surfaces. D. employ countercurrent exchange.
Four of the five structures listed below are common
in mollusks. Select the exception. a. gills b. head and foot c. mantle d. carapace e. radula
While visiting the South Island of New Zealand, you notice that conditions vary sharply across the island. The West Coast is very wet and receives between 600 and 1600 mm of rainfall per year, while the East Coast only receives about 640 mm of rain per year and is very dry. What best explains this regional difference in precipitation?
A. The presence of mountains along the West Coast. B. Proximity to Antarctica. C. The absence of inland lakes. D. The presence of a large river along the West Coast. E. Latitudinal differences between the East and West Coasts.
Which of the following does not occur during M phase in animal cells?
(a) growth of the cell (b) condensation of chromosomes (c) breakdown of nuclear envelope (d) attachment of chromosomes to microtubules