GMAT学习笔记15: SC 11年04月02日回答Jessica001问题记录

28已有 2248 次阅读  2011-06-07 16:23   标签GMAT学习笔记 

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Jessica001

 

According to the passage, the periodic behavior displayed by commuter diatoms under constant laboratory conditions is characterized by which of the following?          

 

A. Greater unpredictability than the corresponding behavior under natural conditions

B. A consistent periodic schedule in the short term

C. No difference over the long term from the corresponding behavior under natural conditions

D. Initial variability caused by the constant conditions of the laboratory

E.Greater sensitivity to environmental factors than is the case under natural conditions

 

Recently biologists have been interested in a tide-associated periodic behavior displayed by the diatom Hantzschia virgata, a microscopic golden-brown alga that inhabits that portion of a shoreline washed by tides (the intertidal zone). Diatoms of this species, sometimes called “commuter” diatoms, remain burrowed in the sand during high tide, and emerge on the sand surface during the daytime low tide. Just before the sand is inundated by the rising tide, the diatoms burrow again.  Some scientists hypothesize that commuter diatoms know that it is low tide because they sense an environmental change, such as an alteration in temperature or a change in pressure caused by tidal movement.  However, when diatoms are observed under constant conditions in a laboratory, they still display periodic behavior, continuing to burrow on schedule for several weeks. This indicates that commuter diatoms, rather than relying on environmental cues to keep time, possess an internal pacemaker or biological clock that enables them to anticipate periodic changes in the environment. A commuter diatom has an unusually accurate biological clock, a consequence of the unrelenting environmental pressures to which it is subjected; any diatoms that do not burrow before the tide arrives are washed away.

 

This is not to suggest that the period of this biological clock is immutably fixed.  Biologists have concluded that even though a diatom does not rely on the environment to keep time, environmental factors—including changes in the tide’s hydrostatic pressure, salinity, mechanical agitation, and temperature—can alter the period of its biological clock according to changes in the tidal cycle.  In short, the relation between an organism’s biological clock and its environment is similar to that between a wristwatch and its owner:  the owner cannot make the watch run faster or slower, but can reset the hands.  However, this relation is complicated in intertidal dwellers such as commuter diatoms by the fact that these organisms are exposed to the solar-day cycle as well as to the tidal cycle, and sometimes display both solar-day and tidal periods in a single behavior. Commuter diatoms, for example, emerge only during those low tides that occur during the day.

 

The answer is B

=.=

Why?

Thx

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Jessica001

顶顶顶@@@@@~~~~ 

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niki.nee

我是新手,我还没仔细研究过OG

我看了看最后也是选的B

我是这样想的,题干出现在“However, when diatoms are observed under constant conditions in a laboratory, they still display periodic behavior, continuing to burrow on schedule for several weeks. ”这句中。这个"however"反驳了上文科学家的假设:这种藻类通过感觉环境变化来“往返”的。这样就排除了E选项;然后这句话中说“still display periodic behavior”,因此往返是有一定规律,的并非不可预测,A选项排除;接着看第二段,大致是讲这种藻类的“往返”规律也是有可能改变的,可能受一些环境因素影响而改变,所以C说不变是不对的;剩下一个D,说是要收到长期的外界改变后,藻类的这种生物钟才会有点调整,它刚到实验室,还水土不服想念大海的时候,咋可能就立马受实验室环境影响改变自己原本作息呢?所以排除。。然后B就对了。。

哎呀哎呀,我解释有漏洞,欢迎各位抨击~  

获积分:36

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Jessica001

short term从哪里可以看出来呀? 

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James

最近生物学家逐渐的对直条菱板藻,一种栖息于常年被潮汐冲刷的海岸线(潮汐区域)的微观金褐色水藻,的与潮汐相关的周期性行为产生了兴趣。这种物种的硅藻,有时也被叫做“上班藻”,一直保持着在涨潮的时候把自己埋在沙中但在白天退潮的时候浮出沙面的特性。仅仅在沙子被潮汐淹没的前夕,硅藻又重新将自己埋在沙中。一些科学家猜想认为上班藻是可以知道潮汐变化的,因为它们可以感受到周围环境的变化,例如温度的改变或者由潮汐活动造成的压力的改变。但是当硅藻被放在实验室的恒定环境中进行观察时,它们仍然表现出周期性的行为特征:按时间把自己埋掉并且持续了好几个星期。这表示上班藻具有一种能够让它们预料环境周期变化的内在的计步器或者生物钟,而不是依赖于环境变化来保证时间。上班藻是有着非同寻常的精确的生物钟的,这是它受制于严酷的环境压力能够成活的一个必然结论:任何在潮汐前没来得及把自己埋掉的硅藻都会被潮水冲走。

这并不是在暗示这种生物钟的周期是固定的。生物学家已经证明尽管硅藻并不依赖环境来计算时间,但是环境因素,包括潮汐的流体压力的改变和温度的改变,都可能改变该生物钟的周期。简单说,有机体的生物钟和外在环境的关系与手表和它的持有者的关系颇为相似:持有者无法将手表调快或者调慢,但是他却可以重新设定手表的指针。但是这些潮汐区域的栖息生物,例如上班藻,同时暴露在潮汐周期和昼夜周期并且有时需要同时表现出两个周期性为这一事实却使得上述关系变得错综复杂。举个例子,上班藻就需要在潮落的白天把自己从沙子里挖出来。

 

根据这篇文章,在稳定的实验室环境下的上班藻的周期性行为可以被描述为:

A 相比于在自然环境下的相应行为有更大的不可预测性

B 在短期内有稳定的周期性时间表

C 相比于在自然环境下的相应行为在长期内都没有任何差别

D 由实验室的稳定环境造成的初始阶段的变化无常

E 相比于自然环境表现出更强的对环境因素的敏感度

 

这道题应该定位于“However, when diatoms are observed under constant conditions in a laboratory, they still display periodic behavior, continuing to burrow on schedule for several weeks. ”这句话的意思是:但是当硅藻被放在实验室的恒定环境中进行观察时,它们仍然表现出周期性的行为特征:按时间把自己埋掉并且持续了好几个星期。

A选项是不对的,事实上上班藻在实验室中的行为表现出了很强的可预测性:“按时间把自己埋掉并且持续了好几个星期。”

B选项是正确的:短期指好几个星期,而不是长期

C选项是不对的,虽然上班藻表现出了相似的行为特性,但是仅仅是在几个星期,所以相比于自然环境绝对不能算长期

D选项是不对的,属于“反”

E选项属于“无”也是不对的

 

B是正确选项。  

获积分:36

 

此问答已经结贴。给积分情况如下: niki.nee: 36个,James: 36  

 

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发表评论 评论 (10 个评论)

  • hsWang 2011-04-06 12:49
    这翻译 这解释  不是一般的水平和耐心能做到的
  • myice 2011-04-06 13:06
    专业
  • James 2011-04-06 13:07
    hsWang: 这翻译 这解释  不是一般的水平和耐心能做到的
    没办法
  • James 2011-04-06 13:08
    myice: 专业
  • stream 2011-04-06 16:58
    敬佩!!学习!!!
  • James 2011-04-06 17:44
    stream: 敬佩!!学习!!!
  • lynljs 2011-06-07 23:04
    这就是那片著名的阅读题哦
  • fyouyang 2011-07-14 12:00
    还以为是句子改错,闹了半天是阅读,直接就跳过了。
  • James 2011-07-15 08:50
    fyouyang: 还以为是句子改错,闹了半天是阅读,直接就跳过了。
    你啥时候考试?
  • fyouyang 2011-07-19 00:50
    James: 你啥时候考试?
    打算8月份请3周假集中准备一下,计划8月20号考。不知到时能否准备好,老板能不能准假。纠结中.......
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