Introduction to Marine Biology

The polyp body plan

A single coral animal is a hollow cylinder with a ring of tentacles around one opening—the mouth is also the exit for waste. Connective tissue links neighbors into a shared colony skin.

Skeleton and tissue layers

Reef builders deposit aragonite beneath the base plate. Living tissue is thin; damage scrapes away protection and exposes skeleton to algae and boring organisms.

Feeding and symbiosis

Zooxanthellae inside gastrodermis recycle nutrients and fuel growth in sunlight; tentacles still capture plankton. That dual nutrition is why shade, sediment, and heat hit corals so hard.

• Label mouth, tentacles, columella, and septa on a diagram for lab.
• Compare solitary vs. colonial tissue layouts.
• Tie structures you memorize here to photos from How to Identify Coral.

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