24th February 2006 at 00:00

Look at photos or images of the animals mentioned or visit a marine aquarium. Find out how the starfish, jellyfish, sessile polyps and sea urchins gather or capture and eat their food. Discuss the features that make these animals suited to a life among coral. For a good selection of drawings, photos and text see


Sample fresh-water ponds and look for living specimens of coral relatives like Hydra and Obelia, or get specimens from a biological supplier. Compare their appearance with that of polyps found in coral. Observe the living specimens with a binocular microscope and look for the bumps that mark the position of the stinging cells (nematocysts) on the tentacles. Add a couple of water fleas or a drop of Marmite to the water and watch how the Hydra or Obelia react.


Compare the symbiotic relationship of zooxanthellae with other examples of mutualism. See Research the integration mechanisms (nerve nets) of the Hydra and corals and compare and contrast them with the simple nervous system found in flatworms.

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