Why does countercurrent exchange optimize gas exchange across some gills?
a. It sustains an optimal thermal environment for gas exchange.
b. It optimizes perfusion to the respiratory surface.
c. It sustains an optimal respiratory gas concentration gradient, allowing diffusion to occur across the entire
respiratory surface.
d. It optimizes delivery of the respiratory medium to the respiratory surface.
e. It minimizes the area of diffusion.
ANSWER: c
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A moss spore develops into a young gametophyte called a(n) ____
a. capsule b. antheridium c. protonema d. prothallus e. archegonium
The small intestine is longer than the large intestine.
Answer the following statement true (T) or false (F)
Differences among organisms are caused by differences in the _____
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