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  3. There is something intrinsically fascinating about the idea of evolution. Wha

There is something intrinsically fascinating about the idea of evolution. Wha

游客2023-12-26  9
问题    There is something intrinsically fascinating about the idea of evolution. What principles govern the evolution of a species? And what does evolution tell us about the place of Homosapiens in the grand order of things? The writer George Bernard Shaw held that a mystical guiding force impels life to evolve toward eventual perfection. Modern scientists may not believe in this guiding force or in the possibility of perfection, but many would agree that life has been improving itself through evolution for billions of years. (Note that this conveniently makes Homosapiens, a very recent product of evolution, one of the newest and most improved versions of life.) In the view of these scientists, constant competition among species is the engine that drives the process of evolution and people’s life upward.
   To Darwin, nature was a surface covered with thousands of sharp wedges, all packed together and jostling for the same space. Those wedges that fared best moved toward the center of the surface, improving their position by knocking other wedges away with violent blows. The standard example that textbooks give of such competitive wedging is the interaction between the brachiopods and the clams. Clams were long held to be ancient undersea competitors of brachiopods due to the fact that the two species inhabited the same ecological niche. Clams are abundant today, whereas brachiopods (dominant in ancient times) are not. Modern clams are also physiologically more complex than brachiopods are. The standard interpretation of these facts is that the clams’ physiology was an evolutionary improvement that gave them the ability to "knock away" the brachiopods.
   In recent years, however, the prominent naturalists Stephen Jay Gould and C. Brad Calloway have challenged the validity of this example as well as the model it was meant to support. Gould and Calloway found that over most geological time clams and brachiopods went their separate ways. Never did the population of brachiopods dip as that of the clams rose, or vice versa. In fact, the two populations often grew simultaneously, which belies the notion that they were fighting fiercely over the same narrow turf and resources. That there are so many more clams than brachiopods today seems rather to be a consequence of mass deaths that occurred in the Permian period. Whatever caused the mass deaths — some scientists theorize that either there were massive ecological or geological changes, or a comet crashed down from the heavens — clams were simply able to weather the storm much better than brachiopods.
   Out of these observations, Gould and Calloway drew a number of far-reaching conclusions. For instance, they suggested that direct competition between species was far less frequent than Darwin thought. Perhaps nature was really a very large surface on which there were very few wedges, and the wedges consequently did not bang incessantly against each other. Perhaps the problem facing these wedges was rather that the surface continually altered its shape, and they had to struggle independently to stay in a good position on the surface as it changed.
   So where does that leave Homosapiens if evolution is a response to sudden, unpredictable and sweeping changes in the environment rather than the result of a perpetual struggle? No longer are we the kings of the mountain who clawed our way to the top by advancing beyond other species. We are instead those who looked to the mountains when floods began to rage below and then discovered that living high up has its definite advantages, so long as our mountain doesn’t decide to turn into a volcano. [br] What is the main idea of the passage?
选项 A、It criticizes Darwin’s evolutionary theory.
B、It discusses a new alternative to an established theory.
C、It examines the nature of the interaction between two species.
D、It demonstrates Gould and Calloway’s conclusions about clams and brachiopods.
答案 B
解析 主旨题。作者并未批评达尔文的进化理论，只是提出不同的看法，所以排除A。达尔文理论中以蛤类和腕足动物为例阐述了楔子模型，但并未研究两者相互作用的性质，所以排除C。第三段阐述了古尔德和卡洛韦关于蛤类和腕足动物的研究发现，只是局部内容，不构成主旨，因此排除D。通观全文，可以看出作者在达尔文进化论的基础上提出了与之有异的古尔德和卡洛韦的进化论，故选B。
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