首页
登录
职称英语
The two claws of the mature American lobster are decidedly different from eac
The two claws of the mature American lobster are decidedly different from eac
游客
2025-04-13
22
管理
问题
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 fight 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 side 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 crasher claws during succeeding stages. An intriguing aspect of this development was discovered by Victor Emmer. 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 later juvenile stage or during adulthood, when asymmetry is present, does not alter the asymmetry; the intact and 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 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 borrowing in the substrate.) Under these conditions, the lobsters developed asymmetric claws, haft 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. [br] 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 ______.
选项
A、likely to be less active
B、likely to be less symmetrical
C、more likely to replace a crusher claw with a cutter claw
D、more likely to regenerate a lost claw
答案
A
解析
由最后一段的内容可知,龙虾触角不对称的形成是在第四和第五期,因为这一时期龙虾的生活环境发生改变,它们开始使用触角工作,而在这之前它们只是被动的随波逐流。
转载请注明原文地址:http://tihaiku.com/zcyy/4036514.html
相关试题推荐
Theideologicalmake-upoftheunionsisnow______differentfromwhatithadbee
EveryoneinAmericanthesedaysseemstobe______withhisorherphysicalfitnes
InAmericanuniversities,classesareoftenarrangedinmoreflexible______andm
ThenewtechnologicalrevolutioninAmericannewspapershasbroughtincreased___
Morethantwopartiesindifferentlocationscantalk______viaaconferencecall
Theideologicalmake-upoftheunionsisnow______differentfromwhatithadbee
Thesystemhasadifferentmoralityasagroupthanthepeopledoasindividuals
Inthepast,Americancollegesanduniversitieswerecreatedtoserveadual
Inthepast,Americancollegesanduniversitieswerecreatedtoserveadual
Americansoftensaythatthereareonlytwothingsapersoncanbesureofi
随机试题
She’llgo______anythingherhusbandsaysjustforaquietandpeacefullife.A、
[originaltext]W:Son,Idon’tknowwhattogetforyourfather.Hehasaboutev
Thechangeinthatvillagewasmiraculou
杀灭幽门螺杆菌,促进溃疡愈合的药物是A.奥美拉唑 B.西咪替丁 C.硫糖铝
为了掌握市场信息,有效安排生产运营,某自行车生产企业进行了市场调查和市场预测活动
下列法律制度中,属于商法领域的有()A.公司法 B.产品质量法 C.破产法
原材料、中间产品一次抽检不合格时,应及时对同一取样批次另取()倍数量进行检
某建设项目,经投资估算确定的工程费用与工程建设其他费用合计为2000万元,项目
动脉粥样硬化症可见A、阿少夫细胞 B、陷窝细胞 C、类上皮细胞 D、泡沫细
对上消化道大出血最有价值的诊断方法是哪项A、临床观察判定 B、吞少量稀钡检查
最新回复
(
0
)