SAT Subject Biology Practice Question 231: Answer and Explanation

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Question: 231

1. Which describes a common difference between terrestrial and aquatic ecosystems?

A. Organisms in terrestrial ecosystems are dependent on oxygen, while those in aquatic ecosystems are not.
B. Nutrients are a limiting factor for populations in aquatic ecosystems but not for terrestrial populations.
C. Producers make up the greatest amount of biomass in terrestrial ecosystems, while in aquatic ecosystems they do not.
D. Sunlight is a limiting factor for populations in terrestrial ecosystems but not for populations in aquatic ecosystems.
E. Energy in aquatic ecosystem is transferred from lower to higher trophic levels, but it moves in the opposite direction in aquatic ecosystems.

Correct Answer: C

Explanation:

Producers in aquatic ecosystems, commonly phytoplankton, do not always make up the greatest amount of biomass. The phytoplankton may be very productive yet consist of a limited number of organisms at any given time.

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