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托福听力练习-科学美国人60秒:公鸡报晓的内时钟

2017-03-15 10:13:00来源：科学美国人60秒

点击查看>>科学美国人60秒音频：公鸡报晓的内时钟

　　科学美国人60秒听力练习：公鸡报晓的内时钟

　　科学美国人60秒英文文本

　　Roosters greet the rising sun with crowing sound. But they also crow at other times. So are they responding to the light? Or do they simply know that it's morning? New research says the latter: roosters crow because of internal time cues. The finding is in the journal Current Biology.

　　Scientists controlled the light levels in rooster habitats. For two weeks, the birds experienced 12 hours of light followed by 12 hours of dim light. Consistent with the pre-dawn noises observed in wild fowl, the roosters began to crow about two hours before their rooms lit up.

　　Then, for two weeks, the roosters lived in constant dim light. Yet they continued to crow about once a day—at intervals of 23.7 hours to be precise. Even without morning light, their circadian rhythms told them when dawn should be breaking.

　　The birds also crowed in response to sudden light, and to the sounds of other roosters. But they were more likely to react when those stimuli occurred near dawn. Showing that you can't really keep a rooster in the dark about the time.

　　中文翻译请点击下一页

本文关键字: 托福听力 科学美国人

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