It can be inferred from the passage that one difference between lobsters in the earlier stages of development and those答案解析-雷哥GRE

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The two claws of the mature American lobster are decidedly different from each other. The crusher claw is short and stout; the cutter claw is long and slender. Such bilateral asymmetry, in which the right side of the body is,in all other respects, a mirror image of the left side,is not unlike handedness in humans. But where the majority of humans are right-handed, in lobsters the crusher claw appears with equal probability on either the right or left side of the body.

Bilateral asymmetry of the claws comes about gradually. In the juvenile fourth and fifth stages of development, the paired claws are symmetrical and cutter like. Asymmetry begins to appear in the juvenile sixth stage of development, and the paired claws further diverge toward well-defined cutter and crusher claws during succeeding stages. An intriguing aspect of this development was discovered by Victor Emmel. He found that if one of the paired claws is removed during the fourth or fifth stage, the intact claw invariably becomes a crusher.while the regenerated claw becomes a cutter. Removal of a claw during a liter juvenile stage or during adulthood, when asymmetry is present,does not alter the asymmetry; the intact and the regenerate claws retain their original structures.

These observations indicate that the conditions that trigger differentiation must operate in a random,manner when the paired claws are intact but in a nonrandom manner when one of the claws is lost. One possible explanation is that differential use of the claws determines their asymmetry. Perhaps the claw that is used more becomes the crusher.This would explain why, when one of the claws is missing during the fourth or fifth stage, the intact claw always becomes a crusher. With two intact claws, initial use of one claw might prompt the animal to use it more than the other throughout the juvenile fourth and fifth stages, causing it to become a crusher.

To test this hypothesis, researchers raised lobsters in the juvenile fourth and fifth stages of development in a laboratory environment in which the lobsters could manipulate oyster chips. (Not coincidentally, at this stage of development lobsters typically change from a habitat where they drift passively, to the ocean floor where they have the opportunity to be more active by burrowing in the substrate.Under these conditions, the lobsters developed asymmetric claws, half with crusher claws on the left, and half with crusher claws on the right. In contrast, when juvenile lobsters were reared in a smooth tank without the oyster chips, the majority developed two cutter claws. This unusual configuration of symmetrical cutter claws did not change when the lobsters were subsequently placed in a manipulatable environment or when they lost and regenerated one or both claws.

It can be inferred from the passage that one difference between lobsters in the earlier stages of development and those in the juvenile fourth and fifth stages is that lobsters in the early stages are

likely to be less active likely to be less symmetrical more likely to lose a claw more likely to replace a crusher claw with a cutter claw more likely to regenerate a lost claw

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当前版本由EMILYSNAIL更新于2019-04-26 16:20:56 感谢由EMILYSNAIL对此题目的解答所做出的贡献。

(Not coincidentally, at this stage of development lobsters typically change from a habitat where they drift passively, to the ocean floor where they have the opportunity to be more active by burrowing in the substrate.Under these conditions, the lobsters developed asymmetric claws.所以问题是在前后passive ACTIVE的区别。所以symmetric的问题，45和6阶段产生

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SHEN_元气森

这也太难了吧，全靠推理没有定位。

6楼 | 2020-12-21 15:46:38 回复

RosieZhang

两空题算短阅读，绝对不可能这么长

5楼 | 2020-09-14 15:47:48 回复

266430ar

用排除法也可以

4楼 | 2020-09-14 08:37:47 回复

哈士奇和鸡阿姨

这些个一上来就要在最后一两段找答案的阅读我真的是脑仁疼，想给一拳暴揍。。。

3楼 | 2020-08-19 18:04:38 回复

158361hil

Not coincidentally, at this stage of development lobsters typically change from a habitat where they drift passively, to the ocean floor where they have the opportunity to be more active by burrowing in the substrate.这一句就说明了在第4/5阶段的发展，会更active，反推就得到以前less active了

2楼 | 2019-09-19 16:56:56 回复

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