GRE阅读真题备考——第三十篇

Passage 30

　　Animals live longer when their calorie intake is restricted to two-thirds of what is considered normal for their species. Animals so restricted are also generally healthier: most disease, including cancer, diabetes, and neurodegenerative illness, are forestalled. (Q2)This phenomenon was long attributed to a simple slowing of metabolism (cells’ production of energy from fuel molecules) and consequent reproduction of its toxic by-products in response to less food. In fact, however, calorie restriction does not slow mammalian metabolism, and (Q1)in yeast and worms, metabolism is both sped up and altered. Some scientists now theorize that calorie restriction is a biological stressor that, like natural food scarcity, induces a more complex defensive response, which in mammals includes changes in cellular defenses and repair.

　　1. In the passage, the function of the highlighted portion is to

　　A. Provide specific examples of organisms whose longevity does not increase in response to calorie restriction.

　　B. Illustrate the probable means by which organisms placed on a calorie-restriction diet compensate for the reduction in available food-based level.

　　C. Suggest the mechanism that is responsible for prolonging the life of organism whose calorie intake is significantly reduced.

　　D. Give an example that explain why scientists’ thinking about the physiological effects of calorie restriction changed.

　　E. Distinguish the different ways that mammalian and non-mammalian metabolisms respond to significant reductions in calorie intake

　　Consider each of the choices separately and select all that apply.

　　2. The passage implies which of the following about the explanation mentioned in the highlighted text?

　　A. There are empirical findings that conflict with a presumption of the explanation.

　　B. The explanation predicts that the effect of calorie restriction on longevity will be the greatest for the species with the highest rate of metabolism.

　　C. The explanation predicts that the effects of calorie restriction will be uniformly positive.

　　答案：D A

以上就是小编为大家带来的历史真题——阅读篇了，希望对大家有所帮助，下载历史真题24套，请点击下方按钮。