Unit 5 Lesson 17
Experience the Great Barrier Reef
The Great Barrier Reef is one of the most amazing ecosystems in the world. It’s so amazing that it is considered to be one of the Seven Wonders of the World. It is teeming with life and has enough color to rival the most breathtaking rainbow. It’s easy to understand why the Great Barrier Reef leaves us in complete admiration. The Great Barrier Reef is one of the Seven Wonders of the World for several reasons.
One of the reasons why people consider the Great Barrier Reef to be one of the Seven Wonders of the World is because of its massive size. It has been recognized as the largest reef system in the world! In fact, it has been measured to be one thousand three hundred miles long. That’s almost twice the length of California! The Great Barrier Reef is so enormous that it can actually be seen from outer space. Contrary to popular belief, the Great Barrier Reef is not one single reef, but consists of about three-thousand individual coral reefs and islands stretching from Cape York all the way to Gladstone near the Queensland coast. Another reason why the Great Barrier Reef is unique is because it is built by tiny living creatures called coral polyps. These cousins of jellyfish have a flowerlike shape. So originally, they were thought to be plants. The size of a coral polyp can range from as tiny as a head of a pin to as big as a dinner plate. These polyps have tube-shaped bodies and mouths that are encircled by tentacles. Polyps can be very subtle creatures, but their tentacles are not. Their tentacles are covered with stinging cells that polyps use to paralyze microscopic animals for food called zooplankton. Then their tentacles gather the food into their mouths. There are polyps that build coral reefs, and they are called stony coral. Stony corals usually live in groups with thousands of other stony corals. By extracting calcium carbonate, stony corals build protective skeletons. When polyps are not feeding they stay in their skeletons. When those polyps die, their bodies perish but their skeletons stay. Then, new polyps grow on top of their ancestors’ carcasses and build their own skeletons. After a long time, all of the skeletons are woven together to form a reef. Certain types of algae grow in between the skeletons, which cements the reef together. The Great Barrier Reef is a fantastic place filled with vibrant color. When you first look at a coral reef, it seems as if the color of stony coral comes from the skeletons, but the skeletons are actually white. The colors come from a layer of coral polyps on the surface. These polyps are clear, but inside of them are millions of microscopic algae cells called zooxanthellae. These algae makes a pigment that makes colors like, red, yellow, blue, and purple, and then these colors show through the polyps’ bodies. To many people who visit the Great Barrier Reef, it is all of the