英语听力：自然百科 澳大利亚大堡礁 Great Barrier Reef—3
时间：2014-05-26 06:15:44
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（单词翻译）
As a polyp grows, it puts up a wall of limestone1 around itself. And then it multiplies. Each polyp can produce thousands of offspring, which all work together to build a living fortress-- a coral reef.
After just a few years, a single piece of coral can harbor as many as 25,000 polyps, all children of the original
founder2. These creatures live fast, but not all die young.
Wachenfeld: “Many corals that help to build the reef only live for a few years, but some, as individual animals, will live for 1000 years or more. These animals are as ancient as any plant or animal on our planet. They are quite incredible.”
Here the polyps have gone into overdrive. They’ve built a reef over 1,200 miles long, enough to stretch from Seattle to Los Angeles. Because in this one spot, a unique combination of circumstances have come together to create a coral heaven.
The whole reef sits on the barely submerged edge of the Australian coast, known as the
continental3 shelf. Other continents have shelves, but none like this. It’s huge, in some places, up to 100 miles wide. On this shelf, it’s summer all year round. Most of all, it’s shallow, so this whole stretch of seabed is blasted in sunlight.
To polyps, light matters as much as warmth, because living within its tissues is a plant.
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