外研版 (2019)选择性必修 第二册Unit 5 A delicate world教案配套ppt课件

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Watch the vide and answer the questins.1 Are humans part f Earth’s ecsystems? Why?2 In what ways can humans affect ecsystems?
Lk at the satellite images and answer the questins.
1 What is happening t the area accrding t the satellite images? 2 What d yu think a later satellite image wuld shw? 3 What d yu think caused these changes?
The water area is shrinking.
The water area will be smaller.
Perhaps because f human ver explitatin.
1 What animals can yu see in the picture? 2 What kind f changes wuld take place if cats, rats and rabbits were intrduced t an envirnment like this?
Read the passage and find ut what happened t Macquarie Island.
I am standing n Macquarie Island, in the Suth-west Pacific Ocean, halfway between Australia and Antarctica. Strng winds and strmy seas have helped sculpt its lng, thin shape. The green grass and bare rck f its landscape cntrast dramatically, giving it a wild and natural beauty. N visitr wuld think it surprising that the island is a UNESCO Wrld Heritage Site. Nr wuld they fail t imagine hw its native inhabitants, including ryal penguins, king penguins, and elephant seals, existed in perfect harmny with their natural habitat fr thusands f years.
But the island’s mre recent histry tells a different stry. It’s a tragic stry that began in 1810 when humans arrived n the island. In their ships they unknwingly brught rats and mice. These small animals quickly tk ver the island, eating the birds’ eggs and attacking baby birds. Cats were brught t the island t cntrl the rats and mice. Unfrtunately, the cats subsequently develped an appetite fr the birds, t.
Meanwhile, rabbits were intrduced t the island as a surce f fd fr humans. Lse n the island, they did what rabbits d best – they multiplied rapidly and began eating the native vegetatin and digging hles, which caused sil ersin. The explding rabbit ppulatin prvided plentiful fd fr the cats, meaning that the number f cats als increased. This in turn led t mre cats hunting the birds. The end result was that parakeets, nce large in number and native t the island, died ut in 1891.
Even after Macquarie Island became an fficial nature reserve in the 1970s, the rabbits remained ut f cntrl. Experts felt it necessary t cme up with a plan t remve all the rabbits frm the island. With this gal in mind, a virus was released nt the island. But althugh the virus caused the rabbit ppulatin t decrease frm 130,000 t arund 10,000, it als meant less fd fr the cats. The cats in cnsequence turned their attentin – and their stmachs – back t the native birds, killing up t 60,000 each year. In the 1980s, traps and dgs were used t catch the cats. The last Macquarie Island cat was caught in 2000.
But as the saying ges, “While the cat’s away, the mice will play.” With the departure f the cats frm the island, the muse and rat ppulatin started t increase. And remember thse 10,000 r s rabbits? It turned ut that they develped an immunity t the virus, and their numbers explded nce again. Then, in 2006, the rabbits’ digging caused sme land t cllapse, and killed a substantial number f penguins. This incident made it clear that the rat, muse and rabbit prblem needed slving nce and fr all.
S, I am here n Macquarie Island t participate in the prgramme t tackle this very prblem. The first step invlved pisn being drpped frm helicpters. The next step is t remve the last remaining invading species, and that’s where I cme in – with my dgs. They have been trained t find every last ne, withut harming the native animals. This interventin is a lng, much-delayed ending t a sad stry, but we humans we it t the island t give it a happy ending.
Pstscript: In 2014, Macquarie Island was declared pest-free and the island’s eclgy is finally n the rad t recvery.
Cats were brught t the island.
Rabbits were intrduced t the island.
T prvide fd fr humans.
they tk ver the island, eating the birds’ eggs and attacking baby birds
The cats develped an appetite fr the birds.
the explding rabbit ppulatin prvided plentiful fd fr the cats. This led t mre cats hunting the birds. As a result, parakeets died ut in 1891.
Nw talk abut hw human interference led t such severe cnsequences fr Macquarie Island.
A virus was released nt the island.
Traps and dgs were used.
Pisn and dgs were used.
T remve all the rabbits frm the island.
T catch the cats.
T remve all the remaining invading species.
The departure f the cats resulted in an increasing ppulatin f rats and mice. And the rabbit ppulatin explded nce again.
The island is pest-free and its eclgy is n the rad t recvery.
Substantial reductin f rabbit ppulatin led t cats killing mre native birds.
1 What is yur understanding f “... we humans we it t the island t give it a happy ending”?2 D yu think it was right t eradicate the “pests” frm Macquarie Island? Give yur reasns.3 Hw culd similar situatins be avided in the future?4 What language can yu use t talk abut cause and effect? Hw wuld yu apply it t yur reading and writing?