（2019新教材）外研版高中英语必修一英语Unit 5　Into the wild学案.doc

1、Unit 5Into the wild 对于动物的灭绝，很多人猜测是气候的原因，其实，有时候 人类才是动物生存最大的威胁。我们要保护动植物，与它们和谐 相处。 Climate change, not human hunting, may have wiped out t he thylacine (袋狼), according to a new study based on DNA from thylacines bones. The meateating marsupials (有袋动物) died out on mainla nd Australia a few thousand year

2、s ago, but survived in Tasman ia, an island of southeast Australia separated from the mainland, until the 1930s. Until then, scientists had believed the cause o f this mainland extinction (灭绝) was increased activity from n ative Australians and dingoes (Australian wild dogs) Scientists behind the Un

3、iversity of Adelaide study, which was published in the Journal of Biogeographyon Thursday, collected 51 new thylacine DNA samples from fossil bones an d museum skins the largest data set of thylacine DNA to d ate. The paper concluded that climate change starting about 4,0 00 years ago in particular

4、drier seasons caused by the weat her systems known as El Nio Southern Oscillation (南方涛动) was likely the main cause of the mainland extinction. The ancient DNA showed that the mainland extinction of t hylacines was rapid, and not the result of loss of genetic diver sity. There was also evidence of a

5、population crash in thylacin es in Tasmania at the same period of time, reducing their num bers and genetic diversity. Associate Professor Jeremy Austin said Tasmania would ha ve been protected from mainland Australias warmer, drier clim ate due to its higher rainfall. He argued that climate change

6、w as “the only thing that could have caused, or at least started, an extinction on the mainland and caused a population crash i n Tasmania.” “They both happened at about the same time, and the ot her two things that had been talked about in the past that may have driven thylacines to extinction on t

7、he mainland were din goes and humans. So the only explanation left is climate chan ge. And because the population crash happened at the same ti me and the species went extinct on the mainland, our argumen t is that theres a common theme there and the only common t heme is that there is this change in climate.”