51 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.
地道英语口语:关于“apple”的英语俚语
新东方英语口语开口篇:Age 年龄(4)
奥运会实用英语口语200句: 我经常用互联网学英语
美国生活必备口语:租房英语大全(1)
大学新生常用口语:熟悉校园和同学
地道口语:如何用英语聊电影
节日英语口语:十一句话搞定圣诞礼物
实用口语情景轻松学:老外和菜农砍价时的地道英语对话
新东方英语口语开口篇:描述外貌(4)
实用口语情景轻松学:你这儿卖内存吗?
口语情景对话:走遍美国精选 当仁不让 ACT 3 - 1
2011年实用口语练习:In the library 在图书馆
实用盘点:赞美他人时必备口语
新东方英语口语开口篇:询问称呼(2)
地道口语:职场必备的五个简单句子
2011年实用口语练习:当死神来临
疯狂口语要素精选 7
实用口语:英语口语要素精选 18
新东方英语口语开口篇:描述外貌(3)
实用口语情景轻松学:你最喜欢哪个季节?
看2012年放假安排:学节日英语对话
20条地道实用英语句型(2)
地道口语:“小气鬼”怎么说?
英语流行语:你跟谁“合得来”?
英语口语主题:交际英语热门话题47个(21--生日派对)
地道口语:用21句表达沮丧
英文情景对话:我想吃真正的中国菜
实用英语:如何用英语砍价
实用口语情景轻松学:说一说旅行要准备的东西
奥运会实用英语口语200句: 你可以乘火车去上海
不限 |
英语教案 |
英语课件 |
英语试题 |
不限 |
不限 |
上册 |
下册 |
不限 |