2. 外语
  3. Extinction is a process that can depend on a variety of ecological, geographical, and physiological variables. These variables a

Extinction is a process that can depend on a variety of ecological, geographical, and physiological variables. These variables a

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问题 Extinction is a process that can depend on a variety of ecological, geographical, and physiological variables. These variables affect different species of organisms in different ways, and should, therefore, yield a random pattern of extinction. However, the fossil record shows that extinction occurs in a surprisingly definite pattern, with many species vanishing at the same time. Which of the following, if true, forms the best basis for at lest a partial explanation of the patterned extinction revealed by the fossil record?
选项 A、Major episodes of extinction can result from widespread environmental disturbances that affect numerous different species.
B、Certain extinction episodes selectively affect organisms with particular sets of characteristics unique to their species.
C、Some species become extinct because of accumulated gradual changes in their local environments.
D、In geologically recent times, for which there is no fossil record, human intervention has changed the pattern of extinction.
E、Species that are widely dispersed are the least likely to become extinct.
答案A
解析 选项(A)，正确答案，指出一些环境变化可以分布非常广，以致造成很多种群的灭绝，这个事实帮助解释了为什么化石记录经常显示许多种群同时灭绝，尽管能造成一个种群灭绝的因素有很多。其他选项中没有一项能解释过去很多种群的灭绝是怎样同时发生的。选项(B)解释了为什么有时只有一些非常有限的种群灭绝了；选项(C)解释了一些个别的种群是如何灭绝的；选项(D)解释了为什么现代时期与化石记录时期不同；选项(E)指出哪些种群最不可能灭绝
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