Biology Test Biology Marine Biology & Aquatic Ecosystems

Question 1

Which zone of the ocean receives enough sunlight to support photosynthesis?

Accepted Answer

Photic (euphotic) zone

Answer

The photic (euphotic) zone extends to about 200 meters depth where sufficient light penetrates for photosynthesis.

Question 2

What are the primary producers in most open-ocean (pelagic) ecosystems?

Accepted Answer

Phytoplankton

Answer

Phytoplankton are microscopic photosynthetic organisms that form the base of the oceanic food web.

Question 3

Coral reefs are built primarily by:

Accepted Answer

Colonial cnidarians secreting calcium carbonate skeletons

Answer

Reef-building (hermatypic) corals are colonial cnidarians that secrete calcium carbonate (aragonite) exoskeletons.

Question 4

Coral bleaching occurs when corals expel their symbiotic algae (zooxanthellae) due to:

Accepted Answer

Elevated water temperatures and stress

Answer

Thermal stress causes corals to expel zooxanthellae, losing their color and primary food source, leading to bleaching and potential death.

Question 5

Which physical factor most strongly stratifies the ocean into distinct layers?

Accepted Answer

Temperature and salinity differences (creating density gradients)

Answer

Differences in temperature and salinity create density gradients that stratify the ocean into the epipelagic, mesopelagic, and deeper zones.

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