2020年9月大学英语六级:2020年6月大学英语六级阅读晨读美文：MarineMammals

【#四六级考试# 导语】没有被折磨的觉悟，就没有向前冲的资格。既然选择了，就算要跪着也要走下去。其实有时候我们还没做就被我们自己吓退了，想要往前走，就不要考虑太多，去做就行了。以下为“2020年6月大学英语六级阅读晨读美文：Marine Mammals”，欢迎阅读参考！更多相关讯息请关注©文档大全网！

　　Since there is such an abundance of food in the sea, it is understandable that some of the efficient, highly adaptable, warm-blooded mammals that evolved on land should have returned to the sea. Those that did have flourished. Within about 50 million years -- no time at all, geologically speaking -- one of the four kinds of mammals that has returned to a marine environment has developed into the largest of all animal forms, the whale. A second kind, the seal, has produced what is probably the greatest population of large carnivorous mammals on Earth. This suggests that these "top dogs" of the ocean are prospering and multiplying. However, such has not been the case, at least not for the last 150 years. Trouble has closed in on these mammals in the form of equally warm-blooded and even more efficient and adaptable predators, humans. At sea, as on land, humans have now positioned themselves on the top of the whole great pyramid of life, and they have caused serious problems for the mammals of the sea. There is a simple reason for this. Marine mammals have the misfortune to be swimming aggregates of commodities that humans want: fur, oil and meat. Even so, they might not be so vulnerable to human depredation if they did not, like humans, reproduce so slowly. Every year humans take more than 50 million tons of fish from the oceans without critically depleting the population of any species. But the slow-breeding mammals of the sea have been all but wiped out by humans seeking to satisfy their wants and whims.

2020年6月大学英语六级阅读晨读美文：Marine Mammals.doc

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