Jellyfish, sea anemones and hydroids are other invertebrate animals that also belong to the Cnidaria group because they have cnidae . Just as there are many species of birds, or fish or insects in the world, so are the species of coral polyps . In the Philippines alone, marine biologists have identified more than 488 different species. In the same manner that birds, fishes or insects have different sizes and colors, so do coral polyps. When coral polyps grow into coral colonies, they form into different shapes depending on what species they are.
Some colonies grow into pointed and hard forms, while others grow round but soft.
The shape, size, and texture of the different corals usually give corals their common name. Some of the most common corals include stony corals, soft corals and horny corals. Scientists use more specific names to identify different types of corals. Examine the different kinds of coral and test each piece of coral for hardness by pounding a few pieces with a rock or hammer. Try to identify the different kinds of coral using the pictures above.