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 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 cutterlike. 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 A. drawing an analogy between asymmetry in lobsters and handed in humans. B. developing a method for predicating whether crusher claws in lobster will appear on the left or right side C. explaining differences between lobsters’ crusher claws and cutter claws D. discussing a possible explanation for the way bilateral asymmetry is determined in lobsters [单项选择]Passage Two
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