In general, the riches of the natural world aren't spread evenly across the globe. Places like

In general, the riches of the natural world aren't spread evenly across the globe. Places like the tropical(热带的) Andes in South America are simply packed with unique species, many of which can't be found in any other places. Until recently, the main explanation for the biological riches concentrated in places like the Amazon Basin was that such places must be engines of biodiversity(生物多样性), with new species evolving(进化) at a faster rate than other parts of the world. But now, new research on bird evolution may turn that assumption on its head, instead supporting the idea that areas with fewer species actually tend to produce new species faster.
The researchers say these biodiversity "coldspots" are generally found in environments featuring freezing, dry and unstable conditions. Though the researchers found these locations with few bird species tend to produce new ones at high rates, they fail to accumulate many species because the unstable conditions frequently make the new life forms die out.
The more well-known "hotspots", by contrast, have accumulated their large numbers of species by being warm, hospitable and relatively stable. Indeed, the researchers found that the countless bird species that call the Amazon home tend to be older in evolutionary terms. "New species do form in places like the Amazon, just not as frequently as in the dry grasslands in the Andes," says Elizabeth, an evolutionary biologist at the University of Tennessee.
The researchers managed to collect 1,940 samples representing 1,287 of the 1,306 bird species from South America. Their analysis showed that the best predictor of whether an area would produce new species at a high rate was how many species lived there, rather than climate or geographic features like mountains. Species-rich areas tended to produce new species more slowly.
"Maybe bad environments generate new species more frequently because there's less competition and more available opportunities for new species," says Gustavo Bravo, a lead researcher.
The study's findings add new urgency to protect ecosystems that may look barren, but may actually be nature's hothouses for the evolution of new species.
28. Why is South America mentioned in the first paragraph?
   A. To make comparison. B. To introduce the topic.
   C. To explain a fact. D. To draw a conclusion.
29. What determines the rising rate of new species in a place?
   A. The number of its then species.      B. The environment they lived in.      
   C. The survival skills of species.       D. The different biological factors.
30. Which of the following can best explain the underlined word “barren” in the last paragraph?
  A. Dry and bare. B. Lively and active.    C. Nice and green.   D. Complex and unpredictable.
31. What might be the best title for the text?
A. Tropical areas are home to large numbers of species.
B. New species prefer to live in the extreme climate.
C. Harsh environments pose a greater threat to species.
D. The worst ecosystem may give birth to new species fastest.
 
28. B   29. A  30. A  31. D
本文是一首说明文,一项新研究表明物种较少的地方比生物多样性丰富的地区更频繁地孕育出新物种。
28. C细节理解题。根据第一段“the main explanation for the biological riches concentrated in places like the Amazon Basin was that they were such place where new species evolved at a faster rate than other parts of the world.(对生物资源集中在亚马逊盆地这样的地方的主要解释是,在这些地方,新物种的进化速度比世界其他地方都快)”可知,之前的解释是亚马孙地区生物多样性丰富是因为该地区新物种进化的速度快。故选C。
29. D细节理解题。根据文章“The more well-known hotspots, by contrast, have accumulated their large numbers of species by being warm, hospitable and relatively stable Indeed, the researchers have found that the countless bird species that call the Amazon home tend to be older in evolutionary terms. (比之下,更为知名的热点地区则因热情好客、相对稳定而积累了大量的物种。事实上,研究人员发现,无数种称亚马逊为家的鸟类在进化上往往更为古老)”可知,亚马逊地区的鸟类较古老是因为该地区宜居,物种不易死亡。故选D项。
30. A推理判断题。根据最后一段 The study’s findings add new urgency for stopping destroying ecosystems that may look dry sand bare, because they may actually be natures hothouses for the evolution of new species.(这项研究的发现为停止破坏那些看起来干燥、光秃禿的生态系统增添了新的紧迫感,因为它们实际上可能是自然界新物种进化的温室)”可推断,研究发现表明,严酷的生态环境有可能是新物种进化的温室,由此可推断,我们应该保护严酷的生态环境。故选A。
31. B主旨大意题。通读全文,根据第一段最后一句“But now, new research on bird evolution may turn that assumption on its head, instead sporting the idea that areas with fewer species actually tend to produce new species faster但现在,有关鸟类进化的新研究可能会推翻这一假设,转而强调物种较少的地区实际上会更快地产生新物种的观点)”可知,本文旨在说明物种较少的地方比生物多样性丰富的地区更频繁地孕育出新物种。故选B。
 
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