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Source: Official Guide Revised GRE 1st Ed. Part 4; Set 4; #3


Which of the following, if true, would help

Which of the following, if true, would help resolve the apparent paradox presented above? During the day in Lake Constance, the zooplankton D. hyalina 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. hyalina. The number of species of zooplankton living at the bottom of the lake is twice that of species living at the surface., Predators of zooplankton, such as whitefish and perch, live and feed near the surface of the lake during the day., In order to make the most of scarce food resources, D. hyalina matures more slowly than D. galeata., D. galeata clusters under vegetation during the hottest part of the day to avoid the Sun’s rays., D. galeata produces twice as many offspring per individual in any given period of time as does D. hyalina.

3 Explanations


Prashant Jha

Yes, it is rather difficult to comprehend initially that both D.hyalina and D. galeata are zooplankton.

Jul 13, 2016 • Comment


Jelly Vora

but option b states that whitefish and perch are predator of zooplankton, so do we have to assume that it feeds galeata alo

Jan 6, 2016 • Comment

Sam Kinsman

Yes, we should. We know that both D. hyalina and D. galeata are zooplankton, so when we're told that whitefish and perch are predators of zooplankton, it's implied that they eat both D. hyalina and D. galeata.

Jan 8, 2016 • Reply

Oscar Nnoli

That's where I found the question confusing too. With the way the paragraph is written, I thought zooplankton was ONLY the D. hyalina species, hence why I didn't pick B. But With this new knowledge, I see now why it's B.

Feb 15, 2016 • Reply


Yes, it's such nice explanation but I felt understand the pattern of question of paradox shift. It's more important. Thank you Sam and Chris!

Sep 11, 2018 • Reply


Chris Lele

Oct 5, 2012 • Comment

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