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PETS背誦閱讀帶翻譯
Marine Mammals
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.
海洋哺乳動(dòng)物 既然海洋中有如此豐富的食物，一些原本在陸地生存的高效率的，適應(yīng)性強(qiáng)的暖血型動(dòng)物返回海洋生存是不難理解的。那些已經(jīng)返回海洋的哺乳動(dòng)物種族繁榮。 在大約 5 千萬(wàn)年 間(這在地質(zhì)學(xué)上不過(guò)是彈指一揮間)，返回海洋的4 種浦乳動(dòng)物之一的鯨已成為體積最龐大 的動(dòng)物。而另一種哺乳動(dòng)物海豹，它的數(shù)量恐怕是地球上大型食肉哺乳動(dòng)物中最大的。 這似乎表明這些海洋中的"大哥大"們?nèi)硕∨d旺，一派繁榮景象。但至少在近 150 年以來(lái)，事實(shí)并非如此。??
同樣是暖血?jiǎng)游锒倚矢�、適應(yīng)性更強(qiáng)的捕食者，人類，成為這些哺乳動(dòng)物的日益迫近的威脅。??
在陸地和海洋，人類都已處在巨大的生物金字塔的最頂端，成為所有生物的主宰，并給海洋哺乳動(dòng)物帶來(lái)巨大的危脅。原因很簡(jiǎn)單。 這些哺乳動(dòng)物不幸成為人類所需要的一堆游動(dòng)著的商品，如皮毛、油和肉。盡管如此，如果它們不象人類一樣繁 殖如此緩慢，它們對(duì)人類的掠奪也不會(huì)如此無(wú)能為力。??
每年人類從海洋中捕撈約 5 千萬(wàn)噸的魚類，但這并未導(dǎo)致任何魚種的滅絕。但繁殖緩慢的海洋哺乳動(dòng)物卻因?yàn)橛辛艘恍闹幌霛M足一已私欲的人類而瀕臨。
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