Australian researchers have discovered electroreceptors (sensory organ

Questions 2 & 5

For Question 2: did you see this post? Check it out and let us know if you have further questions!

For Question 5: Are you asking about how to eliminate (A)? If so, check out this post and see if clears things up. Further explanation of why (E) is the correct answer to question 5 can be found here.

I understand why B is the correct choice for Q2, but am not able to successfully eliminate E. Experts, can you please validate if this reasoning is accurate -

(E) Researchers tested small areas of the anteater???s snout in order to ensure that only electroreceptors were responding to the stimulus.

"The researchers made this discovery by exposing small areas of the snout to extremely weak electrical fields and recording the transmission of resulting nervous activity to the brain."

Passage is backing this idea that small areas of snout were exposed by researchers during their experiment which matches the first half of what's mentioned in choice E which looks correct, but what mainly seems to differ is the reason behind doing this. Paragraph is mentioning that this was done primarily to record neural activity which led them to the discovery of electroreceptors clustered at the tip. Whereas, the second half of choice E distorts the intention of the researchers by saying that the experiment was being done to confirm that only electroreceptors were responding to weak electrical stimuli and nothing else, which is not exactly how it happened and it seems that the choice is mixing the results of the experiment by sounding that it was the cause for this experiment.

Is this correct or am I missing anything here?

That's it! The intention part is the key.

For more on that, check out our explanation here: https://gmatclub.com/forum/australian-r ... l#p3071269.

E is saying "because of the speed, this is not based on chance alone."

Question 1: According to the passage, which of the following is a characteristic that distinguishes electroreceptors from tactile receptors?
Answer: (D) The amount of electrical stimulation required to excite electroreceptors.
Reasoning:

• The passage clearly explains that tactile receptors require electrical field strengths about 1,000 times greater than those needed to excite electroreceptors. This distinction highlights a key characteristic that separates the two sensory organs. This is the best choice because it directly addresses the difference in the electrical stimuli required to activate each type of receptor.

Eliminating other options:

• (A) "The manner in which electroreceptors respond to electrical stimuli": The passage does not describe a difference in how the receptors respond to electrical stimuli, only in the strength of the stimuli required.
• (B) "The tendency of electroreceptors to be found in clusters": While electroreceptors are clustered at the tip of the anteater's snout, this is not the main distinguishing characteristic mentioned in the passage.
• (C) "The unusual locations in which electroreceptors are found in most species": The passage does not provide enough information about the locations of electroreceptors in other species to support this as a distinguishing characteristic.
• (E) "The amount of nervous activity transmitted to the brain by electroreceptors when they are excited": The passage does not focus on differences in the amount of nervous activity transmitted to the brain but rather on the stimuli required to activate the receptors.

Question 2: Which of the following can be inferred about the experiment described in the first paragraph?
Answer: (C) Researchers found that some areas of the anteater’s snout were not sensitive to a weak electrical stimulus.
Reasoning:

• The passage describes how researchers exposed small areas of the anteater's snout to weak electrical fields and recorded the resulting nervous activity. The use of "small areas" suggests that some areas of the snout might not have responded to the stimulus, implying that some regions were not sensitive to weak electrical fields. This supports (C).

Eliminating other options:

• (A) "Researchers had difficulty verifying the existence of electroreceptors in the anteater because electroreceptors respond to such a narrow range of electrical field strengths": The passage does not suggest that electroreceptors respond to a narrow range of electrical field strengths; it only discusses how electroreceptors respond to weaker fields compared to tactile receptors.
• (B) "Researchers found that the level of nervous activity in the anteater’s brain increased dramatically as the strength of the electrical stimulus was increased": While the passage mentions nervous activity, it does not indicate that the level of activity increased dramatically with stronger stimuli.
• (D) "Researchers found that the anteater’s tactile receptors were more easily excited by a strong electrical stimulus than were the electroreceptors": The passage specifically states that tactile receptors respond only to much stronger electrical fields than electroreceptors, making this option incorrect.
• (E) "Researchers tested small areas of the anteater’s snout in order to ensure that only electroreceptors were responding to the stimulus": The passage does not state that the purpose of testing small areas was specifically to isolate electroreceptors; rather, it implies that small areas were tested to observe their response to weak electrical stimuli.

Question 3: The author of the passage most probably discusses the function of tactile receptors (lines 7-11) in order to
Answer: (A) eliminate an alternative explanation of anteaters’ response to electrical stimuli.
Reasoning:

• The author mentions tactile receptors to explain that they can also respond to electrical stimuli, but only in response to much stronger electrical fields than electroreceptors. By highlighting this difference, the author eliminates the possibility that anteaters are responding to the stimuli via tactile receptors rather than electroreceptors. This serves to clarify the distinct role of electroreceptors and eliminate an alternative explanation for the anteater's ability to detect weak electrical fields.

Eliminating other options:

• (B) "highlight a type of sensory organ that has a function identical to that of electroreceptors": Tactile receptors do not have the same function as electroreceptors since they are less sensitive to weak electrical fields.
• (C) "point out a serious complication in the research on electroreceptors in anteaters": The passage does not suggest that tactile receptors create any complications in the research on electroreceptors.
• (D) "suggest that tactile receptors assist electroreceptors in the detection of electrical signals": The passage does not mention any interaction or assistance between tactile receptors and electroreceptors.
• (E) "introduce a factor that was not addressed in the research on electroreceptors in anteaters": Tactile receptors are directly mentioned as a comparative point to electroreceptors, not as an unaddressed factor.

Question 4: Which of the following can be inferred about anteaters from the behavioral experiment mentioned in the second paragraph?
Answer: (C) They can be trained to recognize consistently the presence of a particular stimulus.
Reasoning:

• The passage describes how researchers successfully trained an anteater to distinguish between two troughs of water—one with a weak electrical field and the other with none. This shows that anteaters are capable of being trained to recognize a specific stimulus (the presence of a weak electrical field), which supports the idea that anteaters can consistently recognize such stimuli.

Eliminating other options:

• (A) "They are unable to distinguish between stimuli detected by their electroreceptors and stimuli detected by their tactile receptors": The experiment shows that the anteater can distinguish between the presence of electrical fields, not between different sensory receptors.
• (B) "They are unable to distinguish between the electrical signals emanating from termite mounds and those emanating from ant nests": The passage notes that the researchers have not found electrical signals from termite mounds, but the experiment does not focus on distinguishing between electrical signals from different sources.
• (D) "They react more readily to strong than to weak stimuli": The experiment involved weak electrical fields, and there’s no evidence in the passage that anteaters react more strongly to these weak fields compared to stronger ones.
• (E) "They are more efficient at detecting stimuli in a controlled environment than in a natural environment": The experiment was done in a controlled environment, but the passage does not provide enough information to suggest that anteaters are more efficient in one setting versus another.

Question 5: The passage suggests that the researchers mentioned in the second paragraph who observed anteaters break into a nest of ants would most likely agree with which of the following statements?
Answer: (E) The speed with which the anteaters located their prey is greater than what might be expected on the basis of chance alone.
Reasoning:

• The passage mentions that anteaters quickly located nesting chambers when breaking into ant nests. This suggests that their ability to find prey is not random, but more efficient than what would be expected purely by chance, implying that their electroreceptors are playing a role in this quick and precise location of the prey. Thus, (E) is the most reasonable conclusion.

Eliminating other options:

• (A) "The event they observed provides conclusive evidence that anteaters use their electroreceptors to locate unseen prey": The passage suggests that the anteaters' ability to locate nests is consistent with the hypothesis but does not provide conclusive evidence.
• (B) "The event they observed was atypical and may not reflect the usual hunting practices of anteaters": The passage does not suggest that the behavior of anteaters in the experiment was atypical or unusual.
• (C) "It is likely that the anteaters located the ants’ nesting chambers without the assistance of electroreceptors": The passage implies that the anteaters' behavior is consistent with the use of electroreceptors, making this option unlikely.
• (D) "Anteaters possess a very simple sensory system for use in locating prey": The passage does not describe the anteater’s sensory system as simple; rather, it points to a sophisticated system involving electroreceptors.

Question 6: Which of the following, if true, would most strengthen the hypothesis mentioned in lines 17-19 [Such evidence is consistent with researchers’ hypothesis that anteaters use electroreceptors to detect electrical signals given off by prey]?
Answer: (B) Researchers are able to detect a weak electrical signal emanating from the nesting chamber of an ant colony.
Reasoning:

• The hypothesis in lines 17-19 suggests that anteaters use electroreceptors to detect electrical signals emitted by prey. If researchers were able to detect a weak electrical signal from the nesting chamber of ants, it would support the idea that anteaters are using electroreceptors to detect such signals. This would be direct evidence consistent with the hypothesis.

Eliminating other options:

• (A) "Researchers are able to train anteaters to break into an underground chamber that is emitting a strong electrical signal": While this might suggest that anteaters can detect electrical signals, it does not specifically support the hypothesis about weak electrical signals related to prey detection.
• (C) "Anteaters are observed taking increasingly longer amounts of time to locate the nesting chambers of ants": This would suggest a decline in efficiency, not evidence of electroreceptor use, weakening the hypothesis.
• (D) "Anteaters are observed using various angles to break into nests of ants": This could show different approaches but does not directly support the hypothesis about detecting electrical signals.
• (E) "Anteaters are observed using the same angle used with nests of ants to break into the nests of other types of prey": This does not provide additional evidence for the use of electroreceptors, as it focuses on the angle used in breaking into nests, not the detection of electrical signals.

Hi experts GMATNinja KarishmaB MartyMurray

In question-5, I agree that option A can't be correct but I am also not clear how option E is perfect in itself.

(E) The speed with which the anteaters located their prey is greater than what might be expected on the basis of chance alone

Para 2: Still, researchers have observed anteaters breaking into a nest of ants at an oblique angle and quickly locating nesting chambers. This ability quickly to locate unseen prey suggests, according to the researchers, that the anteaters were using their electroreceptors to locate the nesting chambers.

If we look at the para-2, there is nothing mentioned that "speed" is unique in some way or greater than a speed in a random event for electroreceptors, it is just mentioned that they quickly locate their unseen prey. How can we infer E?

Please help me on this.

Hi All,??
Can someone help to understnad why for Question5 the answer choice is E. I found it option A as logical and thus marked it. Howerver option A is incorrect.

Hi. I see quite a few really good comments in the discussion on page 2 with many experts explaining every single question. I suggest you check it out.