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题库解析   >   主旨题题型   >   RC1-3篇
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454次学习
RC1-3篇

Scientists long believed that two nerve clusters in the human hypothalamus, called suprachiasmatic nuclei (SCNs), were what controlled our circadian rhythms. Those rhythms are the biological cycles that recur approximately every 24 hours in synchronization with the cycle of sunlight and darkness caused by Earth’s rotation. Studies have demonstrated that in some animals, the SCNs control daily fluctuations in blood pressure, body temperature, activity level, and alertness, as well as the nighttime release of the sleep-promoting agent melatonin. Furthermore, cells in the human retina dedicated to transmitting information about light levels to the SCNs have recently been discovered.

Four critical genes governing circadian cycles have been found to be active in every tissue, however, not just the SCNs, of flies, mice, and humans. In addition, when laboratory rats that usually ate at will were fed only once a day, peak activity of a clock gene in their livers shifted by 12 hours, whereas the same clock gene in the SCNs remained synchronized with light cycles. While scientists do not dispute the role of the SCNs in controlling core functions such as the regulation of body temperature and blood pressure, scientists now believe that circadian clocks in other organs and tissues may respond to external cues other than light—including temperature changes—that recur regularly every 24 hours.

【OG20-P398-461题】

The primary purpose of the passage is to


    <p>(A) challenge recent findings that appear to contradict earlier findings</p><p>(B) present two sides of an ongoing scientific debate</p><p>(C) report answers to several questions that have long puzzled researchers</p><p>(D) discuss evidence that has caused a long-standing belief to be revised</p><p>(E)&nbsp;attempt to explain a commonly misunderstood biological phenomenon</p><p><br/></p>
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答案:
D
文章结构 1
Scientists long believed that two nerve clusters in the human hypothalamus,called suprachiasmatic nuclei (SCNs), were what controlled our circadian rhythms. 2 Four critical genes governing circadian cycles have been found to be active in every tissue, however, not just the SCNs, of flies, mice, and humans. 3 While scientists do not dispute the role of the SCNs in controlling core functions such as the regulation of body temperature and blood pressure, scientists now believe that circadian clocks in other organs and tissues may respond to external cues other than light—including temperature changes—that recur regularly every 24 hours. 8.he primary purpose of the passage is to(主旨题) (A) challenge recent findings that appear to contradict earlier findings(与文章结构不符,并不是挑战现在新的发现,而是科学家以前都怎么认为,有了新的证据,科学家的观点进行了点儿修改) (B) present two sides of an ongoing scientific debate(与文章结构不符:首先就不是一个争论) (C) report answers to several questions that have long puzzled researchers(与文章结构不符,不是提出问题,再给出回答,也没有several questions) (D) discuss evidence that has caused a long-standing belief to be revised(与文章结构相符) (E) attempt to explain a commonly misunderstood biological phenomenon (与文章结构不符:首先并不是commonly misubderstood phenomenon,也不是疑惑+试图解释的结构)

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