练习题-2
Part Ⅲ Reading Tasks
True／False／Not Given Exercises
Unit2
When was the last time you saw a frog? Chances are, if you live in a city, you have
not seen one for some time. Even in wet areas once teeming with frogs and toads, it is
becoming less and less easy to find those slimy, hopping and sometimes poisonous
members of the animal kingdom. All over the world, and even in remote parts of Australia,
frogs are losing the ecological battle for survival, and biologists are at a loss to explain
their demise. Are amphibians simply oversensitive to changes in the ecosystem? Could it
be that their rapid decline in numbers is signaling some coming environmental disaster for us all?
This frightening scenario is in part the consequence of a dramatic increase over the
last quarter century in the development of once natural areas of wet marshland; home not
only to frogs but to all manner of wildlife. However, as yet, there are no obvious reasons
why certain frog species are disappearing from rainforests in Australia that have barely
been touched by human hand. The mystery is unsettling to say the least, for it is known that
amphibian species are extremely sensitive to environmental variations in temperature and
moisture levels. The danger is that planet Earth might not only lose a vital link in the
ecological food chain (frogs keep populations of otherwise pestilent insects at manageable
levels), but we might be increasing our output of air pollutants to levels that may have
already become irreversible. Frogs could be inadvertently warning us of a catastrophe.??
An example of a species of frog that, at far as is known, has become extinct, is the
platypus frog. Like the well-known Australian mammal it was named after, it exhibited
some very strange behaviour; instead of giving birth to tadpoles in the water, it raised its
本新闻共4页,当前在第1页 1 2 &n