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Para 1- bilateral asymmetry in American lobster
Para 2- Asymmetry begins to appear in the juvenile sixth stage of development; Victor Emmel's discovery
Para 3- inferences based on VE's discovery; explanation
Para 4- Testing of hypothesis
1. The passage is primarily concerned with(D) discussing a possible explanation for the way bilateral asymmetry is determined in lobsters- Correct
2. Each of the following statements about the development of a lobster’s crusher claw is supported by information in the passage EXCEPT:(A) It can be stopped on one side and begun on the other after the juvenile sixth stage.- Correct
(B) It occurs gradually over a number of stages.- incorrect; 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.
(C) It is initially apparent in the juvenile sixth stage.- - incorrect; 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.
(D) It can occur even when a prospective crusher claw is removed in the juvenile sixth stage.- incorrect, 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.
(E) It is less likely in the absence of a manipulatable environment.- incorrect; In contrast, when juvenile lobsters were reared in a smooth tank without the oyster chips, the majority developed two cutter claws.
3. Which of the following experimental results, if observed, would most clearly contradict the findings of Victor Emmel?(B) A left cutterlike claw is removed in the fourth stage and a crusher claw develops on the left side.- Correct; this is opposite of VE's discovery
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.
4. It can be inferred that of the two laboratory environments mentioned in the passage, the one with oyster chips was designed to(E) simulate the conditions that lobsters encounter in their natural environment
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.)
5. 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(A) likely to be less active
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
6. Which of the following conditions does the passage suggest is a possible cause for the failure of a lobster to develop a crusher claw?(D) Development in an environment devoid of material that can be manipulated
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.
7. The author regards the idea that differentiation is triggered randomly when paired claws remain intact as(B) likely in view of present evidence
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.
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Updated on: 14 Mar 2021, 00:20
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