Animal, mineral, plant?

摘要

How to categorise corals has teased enquiring minds for thousands of years. They have stony, mineral skeletons of calcium carbonate, in effect limestone, and are technically animals. But underwater they resemble shrubs or even flowers, and the cells of many species contain algal symbionts, which make them dependent on light, like plants. This is why they grow in elaborate plant-like shapes to maximise light capture.