Unit 2 Iconic Attractions 单元限时小卷-【高中必刷题】2023-2024学年新教材高中英语选择性必修第四册同步课件（人教版2019）

03 单元限时小卷 建议用时：55分钟 1 [江苏南京六校联合体2023高二期中] Despite the bad reputation of sharks, they are crucial to the health of the marine ecosystem and can even help fight climate change. In the shallows of Shark Bay, Western Australia, seagrass is food for the sea cows, which can weigh as much as 500 kg and eat roughly 40 kg of seagrass a day. Sea cows are a rich source of food for tiger sharks. By keeping the sea cow population in check, tiger sharks in Shark Bay help the seagrass thrive （茁壮成长）. A booming seagrass meadow stores twice as much CO2 per square mile as forests typically do on land. But tiger shark numbers are declining. Off Australia's northeast coast of Queensland, tiger sharks are estimated to have fallen by at least 71 percent, largely due to overfishing. A reduction in tiger sharks means more seagrass is eaten by herbivores （食草动物）, which means less carbon stored in sea vegetation. This raised the question: What if sharks were absent from the Shark Bay—would the seagrass-dominated ecosystem survive? 刷阅读理解 2 To find out, researchers led by Rob Nowicki of Florida International University, spent time in Eastern Australia, where shark numbers were lower and sea cows ate seagrass largely undisturbed. “When unchecked, sea cows can rapidly destroy wide areas of seagrass,” said Nowicki. Those findings emphasised that tiger sharks were playing an important role in preventing the reduction of seagrass in Shark Bay. If shark populations continue to decline, the resilience of carbon-rich ocean ecosystems to extreme climate events like heatwaves will likely to be affected. When it comes to boosting shark numbers, there has been a movement towards more sustainable fishing, but a large percentage of the industry have not changed their methods, which is a reason why the population of many marine top predators （捕食者） continues to decline. Aside from supporting sustainable fishing, Nowicki said the only way to truly protect marine life is to reduce our