高中英语人教版 (2019)必修 第二册Unit 2 Wildlife protection说课课件ppt

这是一份高中英语人教版 (2019)必修 第二册Unit 2 Wildlife protection说课课件ppt，共15页。PPT课件主要包含了读有所获，练有所得，词汇积累，长难句分析，学有所益等内容，欢迎下载使用。

阅读提示：本文为说明文，主题语境为人与自然，主题语境内容为自然环境。地球上的生态系统是如何运转的呢？物种之间有的关系非常紧密，有的关系疏远，科学家用数学模型来弄清生态系统运转的奥秘。本文有助于培养学生的思维品质。
Hw des an ecsystem (生态系统）wrk? What makes the ppulatins f different species the way they are? Why are there s many flies and s few wlves? T find an answer, scientists have built mathematical mdels f fd webs，nting wh eats whm and hw much each ne eats. ① With such mdels, scientists have fund ut sme key principles perating in fd webs. Mst fd webs, fr instance, cnsist f many weak links rather than a few strng nes. When a predatr (掠食动物）always eats huge numbers f a single prey (猎物)，the tw species are strngly linked；when a predatr lives n varius species, they are weakly linked. Fd webs may be dminated by many weak links because that arrangement is mre stable ver the lng term. If a predatr can eat several species, it can survive the extinctin(灭绝）f ne f them. And if a predatr can mve n t anther species that is easier t find when a prey species becmes rare, the switch allws the riginal prey t recver. The weak links may thus keep species frm driving ne anther t extinctin.
Mathematical mdels have als revealed that fd webs may be unstable, where small changes f tp predatrs can lead t big effects thrughut entire ecsystems，In the 1960s, scientists prpsed that predatrs at the tp f a fd web had a surprising amunt f cntrl ver the size f ppulatins f ther species—including species they did nt directly attack. And unplanned human activities have prved the idea f tp-dwn cntrl by tp predatrs t be true. In the cean, we fished fr tp predatrs such as cd n an industrial scale, while n land，we killed ff large predatrs such as wlves. These actins have greatly affected the eclgical balance.
“China is impssible t verlk,”says Hill. “Chinese mdels are the faces f beauty and fashin campaigns that sell dreams t wmen all ver the wrld，which means Chinese wmen are nt just cnsumers f fashin—they are central t its mvement.” Of curse, nt nly are tday’s tp Western designers being influenced by China—sme f the best designers f cntemprary fashin are themselves Chinese. “ Vera Wang, Alexander Wang, Jasn Wu are taking n Gallian, Albaz, Marc Jacbs—and beating them hands dwn in design and sales,”adds Hill.
Scientists have built an early-warning system based n mathematical mdels. Ideally, the system wuld tell us when t adapt human activities that are pushing an ecsystem tward a breakdwn r wuld even allw us t pull an ecsystem back frm the brderline. Preventin is key, scientists say，because nce ecsystems pass their tipping pint (临界点），it is remarkably difficult fr them t return.
What have scientists discvered with the help f mathematical mdels f fd webs?A.Theliving habits f species in fd rules gverning fd webs f the appraches t studying the species in the differences between weak and strng links in fd webs.
Hw des an early-warning system help us maintain the eclgical balance?A.Bygetting illegal practices under stpping us frm killing large bringing the brken-dwn ecsystems back t signaling the urgent need fr taking preventive actin.
A strng link is fund between tw species when a a wide fd chiceB.caneasily find new preyC.Sticks t ne prey speciesD.canquickly mve t anther place
What will happen if the ppulatins f tp predatrs in a fd web greatly decline?A.Theprey species they directly attack will die species they indirectly attack will turn int tp living envirnment f ther species will remain ppulatins f ther species will experience unexpected changes.
What cnclusin can be drawn frm the examples in Paragraph 4?A.Uncntrlledhuman activities greatly upset ecnmic develpment threatens animal f cmmercial value dminate ther activities help keep fd webs stable.