How much of O2 from water flowing over gills is extracted by countercurrent exchange?
a. 50 to 60%
b. 60 to 70%
c. 80 to 90%
d. 90 to 100%
Ans: c. 80 to 90%
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Prokaryotic cells lack
(a) DNA. (b) a true nucleus. (c) a cell wall. (d) none of the above.
What is the function of the bicarbonate ions secreted by the pancreas?
A. to prevent enzymes that digest carbohydrates and fats in the small intestines from becoming denatured B. to stimulate the release of bile from the gall bladder C. to stimulate secretion of the hormone secretin D. to facilitate the transport of nutrients across the intestinal wall E. All of the answer options are correct.
Ecosystem ecology is primarily concerned with
A. ecosystem stability. B. species interactions in various types of ecosystems. C. the synthesis of nutrients. D. patterns of species diversity within ecosystems. E. movement of energy and materials through organisms and their communities.
A decrease in ________ is followed by the gradual degradation of the corpus luteum
A) LH B) FSH C) estrogen D) progesterone