内容正文:
1/6
色学科网书城四
品牌书店,知名教辅+正版资源
b.zxxk.com
您身边的互联网+教辅专家
SectionⅡ课时作业
一、主题下的语篇训练
1.阅读理解
(2023,潍坊模拟)Being taken off the endangered species list doesn't guarantee a carefree
future for whales.Recent research estimates that the population of Pacific gray whales off
North America's West Coast has dwindled by almost a quarter since 2016.Starting in 2019,
alarming numbers of dead gray whales were spotted on beaches and floating offshore
throughout their habitat,from Mexico to Alaska.The National Marine Fisheries Service
defined it as an "Unusual Mortality Event (UME)".UMEs are declared when a "significant
die-off"occurs and when information is collected to clarify why it occurs.
The Arctic has had historically low levels of sea ice in recent years,upending the delicate
ecosystem that sustains gray whales.Like other migrants,they don't feed on their winter
breeding grounds()or along their migration,and must gain weight during the summer
to sustain themselves through the rest of the year.Observers using air photography noted the
whales looked skinnier and arrived in Mexico in poor condition,which suggested they were
not finding enough food during the summer.
This die-off is alarmingly similar to the events of 20 years ago,when another UME
resulted in a significant drop in the gray whale population.Although the cause was ultimately
undetermined,it was thought that the population reached "carrying capacity"-it grew too
large for the environment to support it.Although that idea has been suggested for this die-off
as well,it's more likely blamed on the changing conditions of the Arctic.
Gray whales,hunted almost to extinction by the mid-20th century,were one of the first to
be protected from hunting.The eastern North Pacific population rebounded without pressure
from whaling and was taken off the endangered species list;the western North Pacific
population is still listed as endangered.This die-off is a reminder that "delisting"doesn't
indicate a population's secure future.New threa