Scientists have long known that the soft surface of the bill of the

Question

Scientists have long known that the soft surface of
the bill of the platypus is perforated with openings that
contain sensitive nerve endings. Only recently,
however, have biologists concluded on the basis of new
 (5)  evidence that the animal uses its bill to locate its prey
while underwater, a conclusion suggested by the fact
that the animal’s eyes, ears, and nostrils are sealed
when it is submerged. The new evidence comes from
neurophysiological studies, which have recently
 (10)  revealed that within the pores on the bill there are two
kinds of sensory receptors: mechanoreceptors, which
are tiny pushrods that respond to tactile pressure, and
electroreceptors, which respond to weak electrical
fields. Having discovered that tactile stimulation of the
 (15)  pushrods sends nerve impulses to the brain, where they
evoke an electric potential over an area of the
neocortex much larger than the one stimulated by input
from the limbs, eyes, and ears, Bohringer concluded
that the bill must be the primary sensory organ for the
 (20)  platypus. Her finding was supported by studies
showing that the bill is extraordinarily sensitive to
tactile stimulation: stimulation with a fine glass stylus
sent a signal by way of the fifth cranial nerve to the
neocortex and from there to the motor cortex.
 (25)  Presumably nerve impulses from the motor cortex then
induced a snapping movement of the bill. But
Bohringer’s investigations did not explain how the
animal locates its prey at a distance.

Scheich’s neurophysiological studies contribute to
 (30)  solving this mystery. His initial work showed that
when a platypus feeds, it swims along steadily
wagging its bill from side to side until prey is
encountered. It thereupon switches to searching
behavior, characterized by erratic movements of the
 (35)  bill over a small area at the bottom of a body of water,
which is followed by homing in on the object and
seizing it. In order to determine how the animal senses
prey and then distinguishes it from other objects on the
bottom, Scheich hypothesized that a sensory system
 (40)  based on electroreception similar to that found in
sharks might exist in the platypus. In further
experiments he found he could trigger the switch from
patrolling to searching behavior in the platypus by
creating a dipole electric field in the water with the aid
 (45)  of a small 1.5-volt battery. The platypus, sensitive to
the weak electric current that was created, rapidly
oriented toward the battery at a distance of
10 centimeters and sometimes as much as
30 centimeters. Once the battery was detected, the
 (50) platypus would inevitably attack it as if it were food.
Scheich then discovered that the tail flicks of
freshwater shrimp, a common prey of the platypus, also
produce weak electric fields and elicit an identical
response. Scheich and his colleagues believe that it is
 (55)  reasonable to assume that all the invertebrates on
which the platypus feeds must produce electric fields.   
 1 
 1. The primary purpose of the passage is to

(A) explain how the platypus locates prey at a distance
(B) present some recent scientific research on the function of the platypus’s bill
(C) assess the results of Bohringer’s experimental work about the platypus
(D) present Scheich’s contributions to scientific work about the platypus
(E) describe two different kinds of pores on the platypus’s bill

2 
 2. Which one of the following statements best expresses the main idea of the passage?

(A) Neurophysiological studies have established that the bill of the platypus is one of its primary sensory organs.
(B) Neurophysiological studies have established that the platypus uses its bill to locate its prey underwater.
(C) Bohringer’s neurophysiological studies have established that sensory receptors in the bill of the platypus respond to electrical stimulation.
(D) Biologists have concluded that the surface of the bill of the platypus is perforated with openings that contain sensitive nerve endings.
(E) Biologists have concluded that the hunting platypus responds to weak electric fields emitted by freshwater invertebrates.

3 
 3. During the studies supporting Bohringer’s finding, as they are described in the passage, which one of the following occurred before a nerve impulse reached the motor cortex of the platypus?

(A) The electroreceptors sent the nerve impulse to the fifth cranial nerve.
(B) The neocortex induced a snapping movement of the bill.
(C) The mechanoreceptors sent the nerve impulse via the fifth cranial nerve to the electroreceptors.
(D) The platypus opened the pores on its bill.
(E) The fifth cranial nerve carried the nerve impulse to the neocortex.

4 
 4. Which one of the following strategies is most similar to Scheich’s experimental strategy as it is described in the passage?

(A) To determine the mating habits of birds, a biologist places decoys near the birds’ nests that resemble the birds and emit bird calls.
(B) To determine whether certain animals find their way by listening for echoes to their cries, a biologist plays a tape of the animals’ cries in their vicinity.
(C) To determine whether an animal uses heat sensitivity to detect prey, a biologist places a heat-generating object near the animal’s home.
(D) A fisherman catches fish by dangling in the water rubber replicas of the fishes’ prey that have been scented with fish oil.
(E) A game warden captures an animal by baiting a cage with a piece of meat that the animal will want to eat.

5 
 5. It can be inferred from the passage that during patrolling behavior, the platypus is attempting to

(A) capture prey that it has detected
(B) distinguish one kind of prey from another
(C) detect electric fields produced by potential prey
(D) stimulate its mechanoreceptors
(E) pick up the scent of its prey

6 
 6. Which one of the following best describes the organization of the passage?

(A) A hypothesis is presented and defended with supporting examples.
(B) A conclusion is presented and the information supporting it is provided.
(C) A thesis is presented and defended with an argument.
(D) Opposing views are presented, discussed, and then reconciled.
(E) A theory is proposed, considered, and then amended.

Source:   LSAT Official PrepTest 29   
 Difficulty Level:   600

Anshuman0902 · Answer

sajjad1994 
hello sir !
quiet confuse in q.6 
end up marking d

Sajjad1994 · Answer

Explanation

6. Which one of the following best describes the organization of the passage?

Explanation

As abstract-structure questions go this one is far from the toughest, and that’s because this passage’s structure is close to the simplest: We find out what’s been learned about the platypus’s bill and its hunt for prey  (lines 3-8) , and then find out how scientists arrived at their conclusion.  (B)  has it exactly right.

(A) ’s language about  “supporting examples”  would be more appropriate to a passage about, say, how various sea creatures use their bills to survive. We would hear about the platypus, yes, but also about other creatures and how their behavior bolsters a theory.  “Supporting examples”  carries a different connotation from  “supporting evidence,”  and the latter is what occupies our author’s attention.

(C) “An argument”  is not evidence. This author presents the evidence for a conclusion, as

(B)  says. In any event he has no interest in  “defending”  anything. He is reporting on the work of others.

(D)  No opposing views are laid out and no reconciliation is made. This choice seems to refer to the distinction between Bohringer’s work and Scheich’s, but while we know that their findings may be separate, they are nonetheless complementary rather than in opposition.

(E)  No amendment takes place, at the end of the passage or anywhere else.

Answer: B

Explanation credit: Kaplan LSAT

CEdward · Answer

I thought question 4 was really silly. A number of the options are justifiable and it's not clear what makes one stand out more than the rest.

4. Which one of the following strategies is most similar to Scheich’s experimental strategy as it is described in the passage?

(A) To determine the mating habits of birds, a biologist places decoys near the birds’ nests that resemble the birds and emit bird calls.
Incorrect. "Decoy" is not the same as a battery

(B) To determine whether certain animals find their way by listening for echoes to their cries, a biologist plays a tape of the animals’ cries in their vicinity.
Plausible - the battery functions similarly to a tape - there's some sort of signal being sent

(C) To determine whether an animal uses heat sensitivity to detect prey, a biologist places a heat-generating object near the animal’s home.
Plausible - the battery functions similarly to a heat emitter - there's some sort of signal being sent

(D) A fisherman catches fish by dangling in the water rubber replicas of the fishes’ prey that have been scented with fish oil.
"Rubber replicas" do not function the same way as a battery

(E) A game warden captures an animal by baiting a cage with a piece of meat that the animal will want to eat.
This is based on scent - whereas the platypus uses tactile receptors.

So the question is what makes 'heat' a better choice than 'echoes'? That delineation is not evident in the passage.

Sajjad1994  do you have the answer for this?

Sajjad1994 · Answer

Explanation

4. Which one of the following strategies is most similar to Scheich’s experimental strategy as it is described in the passage?

Difficulty Level:   600

Explanation

This question has a kind of Parallel Reasoning feel to it. We are looking for an experiment analogous with that of Scheich in  Paragraph 2 , which means we need to re-read  lines 41-50 . Placing a small battery in the water triggered a switch in the platypus behavior from  “patrolling”  to  “searching,”  which led Scheich to believe that those bill electroreceptors are sensitive to the electrical charges of prey. Well, if you use electricity to confirm whether an entity senses electricity, what’s the best way to confirm whether an entity senses heat? Use heat.  (C)  has the right analogy.

(A)  goes wrong because of the decoy element: Scheich didn’t put out fake shrimp to lure the platypus.

(B)  errs in its evocation of  “echoes.”  What Scheich is trying to prove is that the platypus senses the electrical impulses of its prey, not that it’s somehow picking up its own electricity by indirection.

(D) , like  (A) , goes wrong in establishing the idea of a decoy or replica.

(E)  would be analogous if Scheich had placed bait in the water to lure the platypus. But he didn’t. He placed a battery—an artificial generator of the same kind of force that, he hypothesized, the prey generates. That’s a far cry from  (E) , but it is  (C)  in a nutshell.

Answer: C

Explanation Credit: Kaplan LSAT

PrachiMaloo · Answer

Can anyone explain question 2 and 3?

Sajjad1994 · Answer

Explanation

2. Which one of the following statements best expresses the main idea of the passage?

Difficulty Level:   750

Explanation

This question piggybacks right onto the previous one. The recent research mentioned in  Q.1 (B)  reveals that the bill is the part of the platypus that locates prey.

(A)  is the conclusion drawn by Bohringer in  lines 18-20  and supported through  line 26.  If that’s the Main Idea, then what are  lines 26-56  there for?

(C)  The electrical stimulation of the bill comes up in  Paragraph 2  only—again, too limited a focus for the Main Idea. We must keep in mind that it’s the use of the bill that concerns both neurophysiologists and our author.

(D)  is something that, according to sentence 1, has been  “long known.”

(E)  is the  “conclusion”  only in the sense that it’s the point at which the passage ends. But  (E) ’s claim about the platypus’s response to electric fields is but one detail in an elaborate process that takes up the entire passage and that is summed up by  (B).

Answer: B

3. During the studies supporting Bohringer’s finding, as they are described in the passage, which one of the following occurred before a nerve impulse reached the motor cortex of the platypus?

Difficulty Level:   600

Explanation

“Which...occurred before” —this question implies that we are to keep an eye on chronology, and on the chronology of  Paragraph 1  because that’s the domain of Bohringer. The language of the question stem appears in  lines 25-26 , and one awesome Sequence Keyword is there to help us:  “Nerve impulses from the motor cortex then” . That  “then”  means that whatever precedes those nerve impulses has to have been described immediately prior to  line 25 , and that’s where we find the substance of  (E) . A signal is  “sent by way of the fifth cranial nerve to the neocortex and from there to the motor cortex.”

(A) , by evoking the fifth cranial nerve, sounds a lot like  (E) , and perhaps if you chose  (A)  it was because you neglected to read  (E)  altogether. That’s a pity, because  (A)  includes a glaring error. Remember, in  Paragraph 1  Bohringer is studying the effect of the mechanoreceptors, the  “pushrods,”  on the platypus’s activity. It is tactile, not electrical, stimulation that  Paragraph 1  and, implicitly, Q. 3 are concerned with. The role of the electroreceptors is the domain of Scheich in  Paragraph 2.

(B)  See  lines 25-26.  The bill’s snapping occurs after—really as a result of—the nerve impulse’s reaching the motor cortex.

(C)  There are those electroreceptors again. They play no role in the Bohringer research in  Paragraph 1 , as far as we know.

(D)  Nothing in the passage indicates that the pores ever  “open”  at all, whether by design or accident.

Answer: E

SofiaDahiya · Answer

Passage summary :  
First author introduces a hypothesis that platypus uses its bill to locate its prey.
Then author mentions neurophysiological studies to provide evidence of sensory receptors within the pores on the bill and Bohringer’s study which supports that bill must be the primary sensory organ for platypus.
In second paragraph, author mentions Scheich’s neurophysiological studies to support the hypothesis that platypus uses its bill to locate its prey.

Hence, we can say that author introduces a hypothesis and different studies to support his hypothesis.

1. The primary purpose of the passage is to

(A) explain how the platypus locates prey at a distance - in 2nd paragraph, author explains this idea using Scheich’s study, hence it mainly covers the scope of 2nd paragraph.
(B) present some recent scientific research on the function of the platypus’s bill -  Author has mentioned multiple studies to support the hypothesis that platypus uses its bill to locate its prey. Hence correct. 
(C) assess the results of Bohringer’s experimental work about the platypus - it's mentioned only in first para
(D) present Scheich’s contributions to scientific work about the platypus - it covers only 2nd paragraph 
(E) describe two different kinds of pores on the platypus’s bill - in first paragraph, author mentions that there are two kinds of sensory receptors. This choice is out of scope.

2. Which one of the following statements best expresses the main idea of the passage?

(A) Neurophysiological studies have established that the bill of the platypus is one of its primary sensory organs. - Bohringer mentioned that the bill must be the primary sensory organ for the platypus, it is not the central idea of the passage.
(B) Neurophysiological studies have established that the platypus uses its bill to locate its prey underwater. -  Author has mentioned multiple studies to support the hypothesis that platypus uses its bill to locate its prey. Hence correct. 
(C) Bohringer’s neurophysiological studies have established that sensory receptors in the bill of the platypus respond to electrical stimulation. - it's not the main idea of the passage
(D) Biologists have concluded that the surface of the bill of the platypus is perforated with openings that contain sensitive nerve endings. - It has been mentioned in first sentence of the passage to introduce the bill in platypus, it's not the main idea of the passage.
(E) Biologists have concluded that the hunting platypus responds to weak electric fields emitted by freshwater invertebrates. - it has been mentioned in support of Scheich’s conclusion, hence it can't be the main idea of the passage

3. During the studies supporting Bohringer’s finding, as they are described in the passage, which one of the following occurred before a nerve impulse reached the motor cortex of the platypus?
 It has been mentioned in the first paragraph that "stimulation with a fine glass stylus sent a signal by way of the fifth cranial nerve to the neocortex and from neocortex to the motor cortex. Nerve impulses from the motor cortex then induced a snapping movement of the bill."

(A) The  electroreceptors  sent the nerve impulse  to  the fifth cranial nerve. - signal was sent "by way of the fifth cranial nerve"
(B) The neocortex induced a snapping movement of the bill. - It happened after nerve impulse reached the motor cortex
(C) The mechanoreceptors sent the nerve impulse via the fifth cranial nerve to the electroreceptors. - mechanoreceptors didn't send the signal to electroreceptors
(D) The platypus opened the pores on its bill. - it's not mentioned anywhere in the passage
(E) The fifth cranial nerve carried the nerve impulse to the neocortex. -  it's mentioned in the sentence above. Signal was sent to neocortex using fifth cranial nerve.

4. Which one of the following strategies is most similar to Scheich’s experimental strategy as it is described in the passage?

Scheich created a dipole electric field in the water, using a small 1.5-volt battery. The platypus, sensitive to the weak electric current that was created, oriented towards battery and attacked it as if it were food.

(A) To determine the mating habits of birds, a biologist places decoys near the birds’ nests that resemble the birds and emit bird calls. - decoy doesn't emit electric field as battery does. Hence Incorrect.
(B) To determine whether certain animals find their way by listening for echoes to their cries, a biologist plays a tape of the animals’ cries in their vicinity. - Tape doesn't emit electric field as battery does. Hence Incorrect.
(C) To determine whether an animal uses heat sensitivity to detect prey, a biologist places a heat-generating object near the animal’s home. -  Heat generating device can be compared to a electric field generating battery, and both have been used to detect prey. Hence correct. 
(D) A fisherman catches fish by dangling in the water rubber replicas of the fishes’ prey that have been scented with fish oil. - Fish oil is not comparable to an electric field generating battery.
(E) A game warden captures an animal by baiting a cage with a piece of meat that the animal will want to eat. - piece of meat is not comparable to an electric field generating battery.

5. It can be inferred from the passage that during patrolling behavior, the platypus is attempting to

(A) capture prey that it has detected - platypus captures the prey after detection, not during patrolling
(B) distinguish one kind of prey from another - nothing is mentioned in the passage about this
(C) detect electric fields produced by potential prey -  it's given in the passage.  
(D) stimulate its mechanoreceptors - mechanoreceptors are used to respond to tactile pressure
(E) pick up the scent of its prey - passage mentions about electric field not about scent

6. Which one of the following best describes the organization of the passage?

(A) A hypothesis is presented and defended with supporting examples. - Author has mentioned a hypothesis, but not provided any example to support that. In fact multiple studies have been mentioned to support the hypothesis.
(B) A conclusion is presented and the information supporting it is provided. -  As author has mentioned multiple studies, we can say that author has mentioned information to support his conclusion. 
(C) A thesis is presented and  defended  with an argument. - Author doesn't defend anything. He just mentions the studies.
(D)  Opposing  views are presented, discussed, and then reconciled. - don't see any opposing views here.
(E) A theory is proposed, considered, and then  amended . - author doesn't amend anything here.

thakurarun85 · Answer

Question number 1 why answer is B. In passage 1 both start and end line is about finding prey and second para is all about finding prey.

Sajjad1994 · Answer

Official Explanation

1. The primary purpose of the passage is to

Difficulty Level:   600

Explanation

The passage lives up to the promise of  lines 3-8 , and that’s just what  (B)  summarizes.

(A), (D)  Both refer only to  Paragraph 2 —to Scheich and the question left open  (lines 26-28)  at the end of  Paragraph 1.

(C) , meanwhile, refers only to  Paragraph 1 . Bohringer no more deserves pride of place in a Global right answer than Scheich does.

(E)  is a purpose taken up and achieved in  lines 10-14  alone. The rest of the passage concerns the function of those pores, the key issue that  (E)  ignores but that  (B)  celebrates.

Answer: B

desertEagle · Answer

Sajjad1994

C says that u r putting heat source near home of animal and not near the animal. What if animal is not home and has gone out. How then is this justifiable

Kindly explain

siddhantvarma · Answer

Passage Breakdown

The passage discusses how the platypus uses its bill to locate prey underwater, focusing on the findings from recent neurophysiological studies.
 
  Introduction of the Platypus's Bill 
 
 The bill has openings with nerve endings. 
 The platypus uses its bill to locate prey underwater since its eyes, ears, and nostrils are closed when submerged.   
  Neurophysiological Studies :
 
 Two types of sensory receptors in the bill:
 
  Mechanoreceptors : Respond to tactile pressure. 
  Electroreceptors : Respond to weak electrical fields.   
 Bohringer's findings:
 
 Tactile stimulation of pushrods sends strong signals to the neocortex. 
 The bill is the primary sensory organ. 
 Stimulation causes the platypus to snap its bill. 
 Bohringer did not explain prey location at a distance.     
  Scheich’s Studies :
 
 Observations of feeding behaviour:
 
 The platypus swims with its bill wagging until it encounters prey. 
 Switches to searching behaviour with erratic bill movements.   
 Hypothesis:
 
 The platypus may have an electroreception system similar to sharks.   
 Conducted an experiments by creating an electric field triggered searching behaviour.
 
 Platypus responded to electric fields from a battery. 
 Platypus attacks the battery as if it were food. 
 Conclusion:
 
 Tail flicks of shrimp produce electric fields, eliciting the same response. 
 Invertebrates that the platypus feeds on likely produce electric fields.        
 Question 5:  It can be inferred from the passage that during patrolling behaviour, the platypus is attempting to

Answer Choices:

(A) capture prey that it has detected

(B) distinguish one kind of prey from another

(C) detect electric fields produced by potential prey

(D) stimulate its mechanoreceptors

(E) pick up the scent of its prey

Answer:

(C) detect electric fields produced by potential prey

Explanation:  The passage describes that during patrolling behaviour, the platypus swims along and wags its bill from side to side. Scheich's studies indicate that the platypus is sensitive to weak electric fields produced by its prey. This suggests that the platypus is trying to detect these electric fields to locate potential prey during patrolling, making option (C) the correct answer.

Question 6:  Which one of the following best describes the organization of the passage?

Answer Choices:

(A) A hypothesis is presented and defended with supporting examples.

(B) A conclusion is presented and the information supporting it is provided.

(C) A thesis is presented and defended with an argument.

(D) Opposing views are presented, discussed, and then reconciled.

(E) A theory is proposed, considered, and then amended.

Answer:

(B) A conclusion is presented and the information supporting it is provided.

Explanation:  The passage begins by discussing the known facts about the platypus's bill and its sensory capabilities. It then presents new conclusions drawn from recent studies, particularly those of Bohringer and Scheich, detailing how the platypus uses its bill to locate prey underwater. The passage provides the experimental evidence and observations that support these new conclusions, thus fitting best with option (B)

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Scientists have long known that the soft surface of the bill of the

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