《2012新课标同步导学英语[外研·全国卷I]必修5课件：6-牵手课堂》由会员分享，可在线阅读，更多相关《2012新课标同步导学英语[外研·全国卷I]必修5课件：6-牵手课堂（9页珍藏版）》请在金锄头文库上搜索。
1、 工具工具工具工具Module 6 Animals in Danger 工具工具工具工具Module 6 Animals in DangerExtinction is for ever! 专专家家指指出出，地地球球上上的的动动植植物物物物种种正正以以前前所所未未有有的的速速度度消消失失，而而无无论论是是它它们们栖栖息息地地的的丧丧失失、污污染染、捕捕猎猎，还还是是全全球球变变暖暖带带来来的的间间接影响，祸根都在于人类。接影响，祸根都在于人类。 工具工具工具工具Module 6 Animals in DangerBefore mans arrival on Earth，species becam
2、e extinct quite naturally. Natural extinction happens when a species decreases in numbers gradually but steadily at the end of its evolutionary (进进化化) period on Earth. The length of this period depends on how well a species can get used to changes around it.This process of extinction can take a very
3、 long timesometimes several million yearsand the extinction of one species is immediately followed by the appearance of another in a continuous cycle. 工具工具工具工具Module 6 Animals in DangerThe case of the dinosaurs is the most wellknown example of natural extinction.They appeared on Earth about 200 mill
4、ion years ago and dominated both land and sea for almost 100 million years.It is not certain why the dinosaurs became extinct，but their disappearance was a natural one and new species of animals evolved to replace them. 工具工具工具工具Module 6 Animals in DangerThe rate of extinction has speeded up unnatura
5、lly over the last 400 years，rising sharply since 1900.This increase in the rate of extinctioh is directly related to the increase in the human population over the same period of time.The great number of humans has caused great damage to the planet.As wild habitats have been taken over，animals and pl
6、ants have been forced into smaller and smaller areas，until some of them have become extinct.We have also polluted some habitats with chemicals and waste，making them unfit for wildlife.These causes of extinction are known as indirect (间接的间接的) destruction. 工具工具工具工具Module 6 Animals in DangerAnimals may
7、 also become extinct through direct destruction.This includes the hunting and catching of animals.Man has always hunted and killed wildlife but early humans lived more in harmony with naturethey killed animals for essential food and clothing.When firearms (火火器器) were invented，great destruction of sp
8、ecies was possible.Animals have been，and still are，killed for meat，clothing，medicines，feathers，eggsand sometimes just for amusement.Some species are still caught in the wild for the live pet trade，even though their numbers are decreasing. 工具工具工具工具Module 6 Animals in DangerThe extinction of at least
9、500 species of animals has been caused by man.Today there are about 5,000 endangered species and at least one species dies out every year.There are probably many more which become extinct without anyone knowing. 工具工具工具工具Module 6 Animals in Danger同学们同学们来学校和回家的路上要注意安全来学校和回家的路上要注意安全 工具工具工具工具Module 6 Animals in Danger同学们同学们来学校和回家的路上要注意安全来学校和回家的路上要注意安全
