During the day in Lake Constance, the zooplankton D. hyaline departs for the depths where food is scarce and the water cold. D. galeata remains near the warm surface where food is abundant. Even though D. galeata grows and reproduces much faster, its population is often outnumbered by D. hyaline.

Which of the following, if true, most helps to resolve the apparent paradox?


A. The number of species of zooplankton living at the bottom of the lake is twice that of species living at the surface.

B. Predators of zooplankton, such as whitefish and perch, live and feed near the surface of the lake during the day.

C. In order to make the most of scarce food resources, D.hyaline matures more slowly than D. galeata.

D. D. galeata clusters under vegetation during the hottest part of the day to avoid the Sun’s rays.

E. D. galeata produces twice as many offspring per individual in any given period of time as does D. hyaline.
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