Photosynthesis Photosynthetic Organisms 3

Question 1

Which photosynthetic organisms are responsible for producing roughly half of Earth's oxygen?

Accepted Answer

Marine phytoplankton

Answer

Marine phytoplankton, including diatoms, dinoflagellates, and cyanobacteria, generate approximately 50% of Earth's oxygen through photosynthesis.

Question 2

Green sulfur bacteria differ from cyanobacteria because they use ______ instead of water as an electron donor.

Accepted Answer

Hydrogen sulfide

Answer

Green sulfur bacteria perform anoxygenic photosynthesis using H2S as the electron donor, releasing sulfur instead of oxygen.

Question 3

What is the term for unicellular photosynthetic organisms that drift in aquatic environments?

Accepted Answer

Phytoplankton

Answer

Phytoplankton are microscopic photosynthetic organisms that float near the water surface where sunlight is available.

Question 4

Dinoflagellates are notable photosynthetic protists that can cause:

Accepted Answer

Coral bleaching and red tides

Answer

Dinoflagellate blooms cause red tides, producing toxins harmful to marine life, and some species cause coral bleaching when they abandon coral hosts.

Question 5

Which photosynthetic symbiont lives inside coral reef organisms and provides them with nutrients?

Accepted Answer

Zooxanthellae (Symbiodinium)

Answer

Zooxanthellae are dinoflagellate algae that live within coral tissues, providing photosynthate in exchange for nutrients and CO2.

Photosynthesis Practice Test