可汗学院
Questions 1-11 are bases on the following passage. The Boreal Chorus Frog: An Exceptional Amphibian?
Over the past decade, a remarkable number of amphibians have come under the threat of extinction. A study conducted by the International Union for Conservation of Nature showed that ①in 2011 the percentage of amphibian species threatened was greater than the percentage of all other species combined This figure marks the largest extinction event since the Pleistocene Era extinctions 10,000 years ago. Several factors contribute to the alarming decline in amphibian ② species; the destruction of habitat, introduction of invasive species, ③contaminating the environment, and rise of infectious diseases.
One amphibian species, though, remains curiously robust. Named for its distinctive breeding call, ④ the habitat of the boreal chorus frog ranges from northern Canada to the American Southwest. One of the most serious threats to amphibians is chytridiomycosis, a disease caused by the chytrid fungus
This fungus is most widespread in the United ⑤States. Specific boreal chorus frog populations studied in Colorado revealed that survival rates have not been seriously affected by the disease. Some studies have also shown that the boreal chorus frog may have a specific advantage in coping with stressors. ⑥ Subsequently, classifying a particular species as robust can be difficult.
[1]Concerning the danger of extinction, amphibians were not ―completely evaluated‖ (more than 90 percent of species assessed) until 2004. [2]In reference to the boreal chorus frog, without this longitudinal data, the natural variability in amphibian reproduction and life histories can mask declines.[3]The main challenge lies ⑦ with a lack of longitudinal data–data collected over an extended period of time. [4]Thus, the boreal chorus frog may simply be in a short robust period and may eventually prove just as susceptible to the threats facing its fellow species. ⑧
What has been made clear from ⑨researcher’s data, and what comprises the key issue in studying amphibians, is the aforementioned number of threatened species. Amphibians play important roles in ecosystems, human health, and commerce. They have ⑩ stuck around for the past 350 millions years, surviving many changes that caused other organisms to become extinct. ⑪ The deterioration of this historically resilient group highlights the importance of the recent studies on threatened amphibians. Ultimately, the boreal chorus frog may prove to be a red herring in a sea of data that points to the need to examine the environmental factors that have caused the current decline in the overall amphibian population.
