英语听力：自然百科 澳大利亚大堡礁 Great Barrier Reef—3

 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.

1 limestone   

n.石灰石

参考例句：

• Limestone is often used in building construction.石灰岩常用于建筑。
• Cement is made from limestone.水泥是由石灰石制成的。

2 Founder   

n.创始者，缔造者

参考例句：

• He was extolled as the founder of their Florentine school.他被称颂为佛罗伦萨画派的鼻祖。
• According to the old tradition,Romulus was the founder of Rome.按照古老的传说，罗穆卢斯是古罗马的建国者。

3 continental   

adj.大陆的，大陆性的，欧洲大陆的

参考例句：

• A continental climate is different from an insular one.大陆性气候不同于岛屿气候。
• The most ancient parts of the continental crust are 4000 million years old.大陆地壳最古老的部分有40亿年历史。