Answer to Question 1ANS: B
The oxygen minimum zone is below the surface zone. Oxygen gets depleted by the animals there, but
is not replaced by photosynthesis. Information can be found in the section Zooplankton Consume
Primary Producers.
Answer to Question 2ANS: D
Krill are considered the keystone of the Antarctic ecosystem. They are the food source for a
tremendous number of animals, including large whales. Information can be found in the section
Zooplankton Consume Primary Producers.