Coral polyps, along with other organisms, have to fight for living space in the complicated environment which they consistently are creating. Coral larvae require a hard surface to attach themselves to. After the baby polyps get settled, they mature into adults and begin to multiply. At some point, there are so many polyps, they start growing right beside or on top of each other. In some cases, it gets so out of control, they begin to latch on anywhere they can find a place.
Initially, corals were categorized as plants. However, as scientific resources became more evolved, microscopic and anatomical research proved that corals were, definitely animals. Just like animal cells, coral cells do not have cell walls. Plant cells do however have cell walls. The lack of cell walls, as well as other criteria, is sufficient enough to categorize corals as animals. Coral reef is extremely beautiful to look at and is one of the biggest attractions in scuba diving and ocean exploration.
Dugongs, manatees, and sea cows
Read more at the list of biomes of the world...