雅思阅读背景知识：雾
随着城市化的进一步加剧，雾这种自然现象变得越来越稀少，回想一下，你上次见到雾是什么时候?想不起来了吧。即使是居住在非常潮湿的地方，雾也变得越来越少，这是为什么呢?我们来看下面的雅思阅读材料。
When was the last time you saw a frog? Chancesare, if you live in a city, you have not seen one forsome time. Even in wet areas once teeming withfrogs and toads, it is becoming less and less easy tofind those slimy, hopping and sometimes poisonousmembers of the animal kingdom.
All over the world, and even in remote parts ofAustralia, frogs are losing the ecological battle for survival, and biologists are at a loss toexplain their demise. Are amphibians simply oversensitive to changes in the ecosystem? Couldit be that their rapid decline in numbers is signaling some coming environmental disaster forus all?
This frightening scenario is in part the consequence of a dramatic increase over the lastquarter century in the development of once natural areas of wet marshland; home not only tofrogs but to all manner of wildlife. However, as yet, there are no obvious reasons why certainfrog species are disappearing from rainforests in Australia that have barely been touched byhuman hand.
The mystery is unsettling to say the least, for it is known that amphibian species areextremely sensitive to environmental variations in temperature and moisture levels. Thedanger is that planet Earth might not only lose a vital link in the ecological food chain (frogskeep populations of otherwise pestilent insects at manageable levels), but we might beincreasing 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 theplatypus frog. Like the well-known Australian mammal it was named after, it exhibited somevery strange behaviour; instead of giving birth to tadpoles in the water, it raised its youngwithin its stomach. The baby frogs were actually born from out of their mother's mouth.Discovered in 1981, less than ten years later the frog had completely vanished from the crystalclear waters of Booloumba Creek near Queensland's Sunshine Coast. Unfortunately, this freakof nature is not the only frog species to have been lost in Australia. Since the 1970s, no lessthan eight others have suffered the same fate.?
One theory that seems to fit the facts concerns the depletion of the ozone layer, a welldocumented phenomenon which has led to a sharp increase in ultraviolet radiation levels.Theozone layer is meant to shield the Earth from UV rays, but increased radiation may be havinga greater effect upon frog populations than previously believed. Another theory is thatworldwide temperature increases are upsetting the breeding cycles of frogs.
TRUE/FALSE/NOT GIVEN
1.Frogs are disappearing only from city areas.
2.Frogs and toads are usually poisonous.
3.Biologists are unable to explain why frogs are dying.
4.The frogs' natural habitat is becoming more and more developed.
5.Attempts are being made to halt the development of wet marshland.
6.Frogs are important in the ecosystem because they control pests.
7.The platypus frog became extinct by 1991.
8.Frogs usually give birth to their young in an underwater nest.
9.Eight frog species have become extinct so far in Australia.
10.There is convincing evidence that the ozone layer is being depleted.11.It is a fact thatfrogs' breeding cycles are upset by worldwide in creases in temperature.
Answer Keys
1.F 2.F 3.T 4.T 5.NG 6.T 7.T 8.NG 9.F 10.T 11.F
以上就是为大家整理的雅思阅读背景知识：雾，希望通过这些背景知识的复习，能够让大家在阅读考试中取得好成绩。