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2015考研英语模拟试题：阅读理解
以下是[无&忧考&网]为大家整理的关于2015考研英语模拟试题：阅读理解的文章，供广大考生查阅！！Flatfish, such as the flounder, are among the few vertebrates that lack approximate bilateral symmetry (symmetry in which structures to the left and right of the body’s midline are mirror images). Most striking among the many asymmetries evident in an adult flatfish is eye placement: before maturity one eye migrates, so that in an adult flatfish both eyes are on the same side of the head. While in most species with asymmetries virtually all adults share the same asymmetry, members of the starry flounder species can be either lefteyed (both eyes on the left side of head) or righteyed. In the waters between the United States and Japan, the starry flounder populations vary from about 50 percent lefteyed off the United States West Coast, through about 70 percent lefteyed halfway between the United States and Japan, to nearly 100 percent lefteyed off the Japanese coast.
Biologists call this kind of gradual variation over a certain geographic range a “cline” and interpret clines as strong indications that the variation is adaptive, a response to environmental differences. For the starry flounder this interpretation implies that a geometric difference (between fish that are mirror images of one another) is adaptive, that lefteyedness in the Japanese starry flounder has been selected for, w