issue121 ugw战队2号第二十次作业

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121. "At various times in the geological past, many species have become extinct as a result of natural, rather than human, processes. Thus, there is no justification for society to make extraordinary efforts, especially at a great cost in money and jobs, to save endangered species."
在过去不同的地质时期，许多的物种因为自然作用而非人类行为而灭绝。因此，人类社会为了挽救濒危物种而付出的巨大努力，尤其是以大量的资金和工作机会为代价，这样做是毫无道理的。

提纲：
1、生物史上许多动物灭绝与人类无关；
2 、随着打猎工具的发展以及对环境的破坏，人类对动物生存的威胁增大；
3、 即使有些动物的濒危是由于自身因素，人类为了物种多样性的维持也应该挽救这些物种   

     Should society stop making efforts to save endangered species? The speaker claims so, for the reason that many species have been extinct as a result of natural. I concede it is true in the past, but today, with actions that destroy environment and development of tools used in hunting, people largely threat the survival of wild animals and should pay attention to save endangered species.

     In the first place, it is no doubt that, throughout history of biology, there were so many species having become extinct as a result of natural rather than human processes. One example in case, the reason of the extinction of dinosaurs, which once ruled earth for quite a long time, is still not certain today. But it is obvious that their eliminating had no relationship to human for last dinosaurs lived about 50 millions years before earliest human beings. Another example is the extinction of mammoths, which happened about twenty thousand years ago, although there had been human beings at that time, but without the powerful strength as us today, they can hardly affect the environment of earth and it has been proved that mammoth's extinction mainly due to their huge body which appeared to become burden at the ice age. In conclusion, it is true that human beings have nothing to do with some species' eliminating in the geological past.
     
     But, we can not negative that with the development of human society, human today can affect the survival of wild animals to a far greater extent than ancestors did. With improvement in tools used in hunting, people can do hunting more efficiently. As an illustration, antelopes run very fast so they are hard to be hunted before guns invented. But today, with accurate guns, hunters can do their job more easily, and the number of the wild antelopes has decreased fast in recent centuries. More over, people today can not only hunt animals so that affect their survival in a direct way, but also can destroy the environment so as to threat wild animal indirectly. All means today, human beings should take the responsibility to save animals in danger so as to keep the delicate balance upon which all animals depend.

     And even if some animals are in danger due to their own factors; human beings should try their best to save them, for it is important to sustain the variety of species. As an illustration, there are only about one thousand pandas throughout the world, and it is their low ability of propagating not other factors that makes them in danger, although human needn't be blamed for the extinction of pandas, we should still make efforts to carry out saving work, not only for pandas, but also for our generation and the variety of species.

     In sum, many species' eliminating in the geological past were caused by nature factors and had no relationship to human, but today, with being more powerful than ever before, people can largely determine the destiny of wild animals. And human should try their best to prevent the balance of biosphere from being broken.