Zooxanthellae are symbiotic algae that reside in the tissues of which organisms?

Zooxanthellae are symbiotic algae that reside in the tissues of which organisms?

• A. Echinoderms
• B. Cnidarians such as corals
• C. Porifera
• D. Tunicates

Answer: (B)

Photosynthetic algae living inside coral tissues form a mutualistic association that is essential for reef-building corals. The zooxanthellae provide energy-rich organic carbon produced by photosynthesis, which fuels coral growth and the production of calcium carbonate skeletons. In return, the coral offers a protected environment and waste products like CO2 and nutrients that the algae use. This partnership is characteristic of cnidarians, including corals and some sea anemones, and is not typical of echinoderms, sponges, or tunicates. Bleaching occurs when environmental stress causes the algae to be expelled, weakening the coral.

Photosynthetic algae living inside coral tissues form a mutualistic association that is essential for reef-building corals. The zooxanthellae provide energy-rich organic carbon produced by photosynthesis, which fuels coral growth and the production of calcium carbonate skeletons. In return, the coral offers a protected environment and waste products like CO2 and nutrients that the algae use. This partnership is characteristic of cnidarians, including corals and some sea anemones, and is not typical of echinoderms, sponges, or tunicates. Bleaching occurs when environmental stress causes the algae to be expelled, weakening the coral.