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SAMPLE 12 [生物学类] 题目序号 题型归类 第1题 细节推导题型 第2题 写作手法题型 第3题 审题定位与中心主旨题型 第4题 词汇题型 第5题 审题定位题型 Flatfish, such as the flounder, are among the few vertebrates that lackapproximate bilateral symmetry . Most striking among the many asymmetriesevident in an adult flatfish is eye placement: before maturity one eyemigrates, so that in an adult flatfish both eyes are on the same side of thehead. While in most species with asymmetries virtually all adults share thesame asymmetry, members of the starry flounder species can be either left-eyed or right-eyed. In the waters between theUnited States and Japan, the starry flounder populations vary from about 50percent left-eyed off the United States West Coast, through about 70 percentleft-eyed halfway between the United States and Japan, to nearly 100 percentleft-eyed off the Japanese coast. Biologists call this kind of gradual variation over a certain geographicrange a cline and interpret clines as strong indications that the variation isadaptive, a response to environmental differences. For the starry flounder thisinterpretation implies that a geometric difference is adaptive, that left-eyedness in the Japanesestarry flounder has been selected for, which provokes a perplexing question:what is the selective advantage in having both eyes on one side rather than onthe other? | 
