Unit 5 Revealing Nature-【红对勾讲与练】2022-2023学年新教材高中英语选择性必修第一册(外研版)

Unit 5　 Revealing nature 课时作业 13 　 　 　 　 　 　 　 　 　 　 　阅读理解 A A dragonfly barely an inch and a half long appears to be the animal world􀆳s most productive long distance traveler—flying thousands of miles over oceans as it migrates from continent to conti- nent—according to a newly published research. Biologists who led the study say the evidence is in the genes. They found that populations of this dragonfly, called Pantala flavescens, in Texas, eastern Canada, Japan, Korea, India, and South America, have genes so similar that there is only one likely explanation. Apparently— somehow—these insects are travelling distances that are extraordinarily long for their small size, breeding ( 繁殖) with each other, and creating a common worldwide gene pool. But how do insects from different continents manage to meet and hook up? Ware says it appears to be the way their bodies have evolved. “ These dragonflies have adaptations such as increased surface areas on their wings that enable them to use the wind to carry them. ” Dragonflies, in fact, have already been observed crossing the Indian Ocean from Asia to Africa. “They are following the weather,” says Daniel Troast, who analyzed the DNA samples in Ware􀆳s lab. “ They􀆳re going from India where it􀆳s the dry season to Africa where it􀆳s the wet season, and apparently they do it once a year. ” Wetness is a must for Pantala to reproduce, and that, says Ware, is why these insects would be driven to even attempt such a dangerous trip, which she calls a “kind of suic