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Dinosaurs
Temat: Nauka i technologia
Do some Exercises: Słuchaj i zapisuj Tworzenie zdań Ukryte słowa
DOUG JOHNSON: Welcome to American Mosaic in VOA Special English. I'm Doug Johnson. Today we answer a question about dinosaurs. DOUG JOHNSON: Our listener question this week comes from Sarah Sun in China. She says she is nine years old and has liked dinosaurs since she was six. She wants to know the latest dinosaur news. We found an interesting story on the Discovery News website. It tells about how dinosaurs became such large animals. The simple answer is: they ate a lot of food. Some dinosaurs ate meat and some ate only plants. But scientists found that it is not just what they ate. Their large size was affected by how they ate it. Dinosaurs died out millions of years ago. So we have only their bones, or fossils, to study. But there is one animal on Earth today that may help scientists learn about dinosaurs. That animal is the elephant. The elephant needs to eat for about eighteen hours each day in order for it to grow as large as it does. Many dinosaurs were much larger than today's elephant. How much time did they spend each day eating their food? Scientists think the largest dinosaurs would have to have spent thirty hours a day chewing and swallowing their food. And that is a problem since there are only twenty-four hours in a day. So how could dinosaurs have been able to eat enough to stay alive? According to the journal Biological Reviews, most dinosaurs did not take the time to chew their food. They swallowed it whole. Their teeth were used to rip the meat or plants into mouth-sized pieces, but were not used for chewing. Chewing takes time and energy which a dinosaur could not waste. But not all dinosaurs were huge like the famous Tyrannosaurus or Brontosaurus. Some were much more like birds. The idea that dinosaurs and birds were somehow related first was reported in the nineteenth century. But only recently has their relationship become clearer. There have been many new dinosaur discoveries in China and Mongolia. Many of these animals had feathers, much like our modern birds. But scientists think the dinosaurs developed feathers first, and then wings. If that is correct, the first bird-like dinosaurs did not fly. They soared or glided through the air. Source: Voice of America
