SAT Subject Biology Practice Question 68: Answer and Explanation

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Question: 68

2. The net primary production (NPP) of a stable lake ecosystem is roughly equal to the amount of

A. phytoplankton present in the photic zone
B. phytoplankton consumed by heterotrophs
C. dissolved nutrients used by phytoplankton
D. dissolved oxygen used by phytoplankton
E. dissolved oxygen used by all consumers

Correct Answer: B

Explanation:

NPP is not equal to the total biomass of producers, but to the amount of biomass that is added. In a stable lake, the added phytoplankton biomass will equal that consumed by zooplankton.

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