48 Protected by Armor

Where can you find a cliff built entirely by animals? On the bottom of the ocean! Underwater reefs are huge walls made by tiny animals called corals. Because corals are very small, reefs take hundreds of years to build.

How do such small animals accomplish such a great task? The answer is simple. The reefs are composed of coral polyps. They are small animals called “polyps.” They have very soft bodies. Without some kind of “armor,” they would be eaten by fish. To protect themselves, they build limestone shells around their bodies.

Coral polyps live in colonies. They connect themselves to each other and to the ocean floor. The corals build their limestone skeletons by taking a mineral called calcium out of the water and depositing it around themselves. The calcium deposits are very hard. As new polyps are born and attach themselves to the colony, the formation gets bigger. After a long time, a large reef has grown up.

The world’s largest coral reef is longer than the state of New York. It is the Great Barrier Reef of Australia.

48 身披铠甲的保护

你能在哪里找到完全由动物建造的悬崖呢？在海洋的底部！水下珊瑚礁是由被称为珊瑚的微小动物建造的巨大岩壁。因为珊瑚非常小，珊瑚礁的形成需要数百年的时间。

这么小的动物是如何完成如此伟大的任务的呢？答案很简单。珊瑚礁由珊瑚虫组成，这些小动物被称为“珊瑚虫”。它们的身体非常柔软，如果没有某种“铠甲”，就会被鱼吃掉。为了保护自己，它们在身体周围建造了石灰岩外壳。

珊瑚虫群居生活，它们相互连接，并与海底相连。珊瑚通过从水中提取一种叫做钙的矿物质，并将其沉积在自己周围，来构建石灰岩骨架。钙沉积物非常坚硬。随着新的珊瑚虫诞生并附着在群体上，珊瑚礁的结构变得越来越大。经过很长时间，就形成了一个大的珊瑚礁。

世界上最大的珊瑚礁比纽约州还长，它就是澳大利亚的大堡礁。