Bunuel wrote:
Certain groups of Asian snails include both “left-handed” and “right-handed” species, with shells coiling to the left and right, respectively. Some left-handed species have evolved from right-handed ones. Also, researchers found that snail-eating snakes in the same habitat have asymmetrical jaws, allowing them to grasp right-handed snail shells more easily. If these snakes ate more right-handed snails over time, this would have given left-handed snails an evolutionary advantage over right-handed snails, with the left-handed snails eventually becoming a new species. Thus, the snakes' asymmetrical jaws probably helped drive the emergence of the left-handed snail species.
Which of the following would, if true, most strengthen the argument that asymmetrical snake jaws helped drive left-handed snail evolution?
A. In one snake species, the snakes with asymmetrical jaws eat snails, while the snakes with symmetrical jaws do not eat snails.
B. Some species of Asian snails contain either all right-handed snails, or all left-handed snails.
C. Anatomical differences prevent left-handed snails from mating easily with right-handed snails.
D. Some right-handed snails in this habitat have shells with a very narrow opening that helps prevent snakes from extracting the snails from inside their shells.
E. Experiments show that the snail-eating snakes in this habitat fail more often in trying to eat left-handed snails than in trying to eat right-handed snails.
CR32441.01
OG2020 NEW QUESTION
Understanding the passageCertain groups of Asian snails include both “left-handed” and “right-handed” species, with shells coiling to the left and right, respectively.
• There are certain groups of Asian snails which include both species, left-handed and right-handed snails.
• Left-handed snails are snails with shells coiling to the left, and Right-handed snails are snails with shells coiling to the right.
Some left-handed species have evolved from right-handed ones.
• Some of the left-handed species of snails have evolved from the right-handed species.
Also, researchers found that snail-eating snakes in the same habitat have asymmetrical jaws, allowing them to grasp right-handed snail shells more easily.
• Additionally, researchers found that a particular species of snake, which is the snail-eating snake, had asymmetrical jaws.
• The asymmetrical jaws in snail-eating snakes help them grasp right-handed snails shells more easily.
• Inference: It is less easy or difficult to grasp left-handed snails shells for snail-eating snakes with asymmetrical jaws.
If these snakes ate more right-handed snails over time, this would have given left-handed snails an evolutionary advantage over right-handed snails, with the left-handed snails eventually becoming a new species.
• Since snail-eating snakes find it easier to grasp right-handed snails shells, it would mean that catching right-handed snails is easier for these species of snakes.
• Therefore, this could mean that these snakes consume more right-handed snails over time, giving an evolutionary advantage to left-handed snails.
• This advantage for the left-handed snails can lead them to become a new species.
Thus, the snakes' asymmetrical jaws probably helped drive the emergence of the left-handed snail species.
• Therefore, the snakes’ asymmetrical jaws are likely responsible for the rise of left-handed snail species.
Conclusion: The snakes' asymmetrical jaws probably helped drive the emergence of the left-handed snail species.
Pre-thinkingStrengthen Framework
What information will help us believe more in the conclusion?
Conclusion: The snakes' asymmetrical jaws probably helped drive the emergence of the left-handed snail species.
Given that:(i) Left-handed snails are snails with shells coiling to the left, and Right-handed snails are snails with shells coiling to the right.
(ii) Snail-eating snakes have asymmetrical jaws.
(iii) The asymmetrical jaws in snail-eating snakes help them grasp right-coiled snails shells more easily.
(iv) If snail-eating snakes consumed more right-coiled snails, then this could give an advantage to left-coiled snakes and can lead them to become a new species.
Thought Process
There are both Asian snails with shells that coil to the right and Asian snails with shells that coil to the left, and the latter have evolved from the former; furthermore, there are snakes that have asymmetrical jaws that allow the snakes to grasp the snails with right-coiled shells more easily.
Strengthener
Since we are told that if over time the snakes with asymmetrical jaws ate more snails with right-coiled shells than snails with left-coiled shells, then this would give snails with left-coiled shells an evolutionary survival advantage
A statement that indicates that the snakes with asymmetrical jaws, in fact, were more likely to have successfully eaten the snails with the right-coiled shells, then we would have good reason to think the snakes' asymmetrical jaws helped drive the emergence of snails with left-coiled shells.
Answer Choice AnalysisA. In one snake species, the snakes with asymmetrical jaws eat snails, while the snakes with symmetrical jaws do not eat snails.
INCORRECT• The fact that snakes with asymmetrical jaws eat snails and other snakes do not give any indication as to whether snails with left-coiled shells have any evolutionary advantages over snails with right-coiled shells. Thus, this choice is incorrect.
B. Some species of Asian snails contain either all right-handed snails, or all left-handed snails.
INCORRECT• The information in this statement is irrelevant to the conclusion because it does not tell us whether they have any evolutionary advantages over other snails, or whether the snakes' asymmetrical jaws had any effect on any such evolutionary advantages.
• Thus, this is not the correct choice.
C. Anatomical differences prevent left-handed snails from mating easily with right-handed snails.
INCORRECT• Mating of left-handed snails with right-handed snails will not have any impact on the conclusion of the passage. Thus, the information present in the statement is irrelevant, and this is not the correct choice.
D. Some right-handed snails in this habitat have shells with a very narrow opening that helps prevent snakes from extracting the snails from inside their shells.
INCORRECT• This statement will weaken the conclusion.
• The fact that snakes cannot extract some snails with right-coiled shells from their shells would suggest that these snails might have an evolutionary advantage, but the author's conclusion is about an evolutionary advantage that snails with left-coiled shells possibly have, not an advantage that snails with right-coiled shells would have.
E. Experiments show that the snail-eating snakes in this habitat fail more often in trying to eat left-handed snails than in trying to eat right-handed snails.
CORRECT• The fact that experiments show that the snakes are more successful at eating snails with right-coiled shells than they are at eating snails with left-coiled shells would support the author’s conclusion. Therefore, this is the correct choice.
Cheers!