在奥陶纪，大多数生命都生活在海洋里，所以海洋生物，例如三叶虫、腕足类动物与笔石动物的数量在此时急剧减少。

During the Ordovician, most life was in the sea, so it was sea creatures such as trilobites, brachiopods and graptolites that were drastically reduced in number.

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他们认为，近年来，许多动物物种数量的急剧减少，像青蛙、鱼类和老虎等等，其锐减速度赶得上过去5亿4千万年以来五次大规模物种灭绝的任意一次。

They believe that the steep decline in populations of many animal species, from frogs and fish to tigers, is as fast as any of the last five extinctions in the past 540 million years.

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在一些地区，金丝燕数量已经急剧减少，动物保护官员不得不想方设法来保护它们。

Swiftlet populations have fallen steeply in some regions, prompting conservation officials to look for ways to protect the species.

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