For this passage, the answers are in the details. A good strategy, like with most GMAT RC passages, is to create an outline in your head, encapsulating the main points of the passage:

OTs forage throughout lactation period (last up to 3 yrs)
PH. are larger and were thought to fast during their much shorter lactation periods.

Harbor seal, PH., challenges this traditional view, since it forages during lactation.

Possible theory: the harbor seal is much smaller than average PH, which have lots of blubber and can fast,
and is similar in size to OT, which don't have much fat stores.

Size is connected to foraging behavior and lactation.

Now to the questions

1) Otariids have a lactation period that is "4 months to 3 years"; phocines have one that "lasts from 4 and 50 days. Therefore, (A).

2) Harbor seals feed during lactation, which is uncommon in phocines (the second passage contrasts the grey seal, a phocine, which fasts throughout lactation). The point of the passage is to account for this behavior (the theory is that size plays a major role in lactation and foraging). The first paragraph mainly provides context for the difference between the two seal species in this regard.

(C) shifts the focus to current theories on harbor seals and how these theories are incorrect. The point of the passage is that the harbor seal represents an instance that should lead experts to reconsider their views on phocine as a whole, when it comes to foraging and lactation.

(E) goes too far since the passage never implies that the harbor seals belongs to the otariids, just that its behavior is atypical for a phocine, and therefore that not all phocine follow a pattern similar to that of the grey seal.

3) The last part of the first paragraph points to the idea that zoologists thought that all phocines fast throughout lactation, "fasting strategy in which mother phocids, having accumulated large energy stores before they arrive at breeding sites, fast throughout the entire lactation period". The "however" clues us into the fact that the behavior of the harbor seal changes this view.

4) The last part of the second paragraph arrives at the conclusion that the foraging behavior of the harbor seal is related to its size. To further back up this claim, the passage mentions the "ring seal", another small phocine that has similar foraging behavior during lactation as the harbor seal. The phrase "maternal strategy" represents foraging and lactation behavior.


Hope that helps
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6 min 18 secs - Answered all questions correctly.

1) It can be inferred from the passage that the females of all phocid species differ from the females of all otariid species in that the female phocids

Lactation period of otarids - 4 months to 3 yrs
Lactation period of phocids - 4 days to 50 days

Answer: A

2) The primary purpose of the passage is to

The passage first distinguishes between the maternal strategy of otarids and phocids. Next, the passage takes up the example of harbor seals, a phocid which does not follow the phocid maternal strategy. The passage explains possible reasons for the behavior exhibited by harbor seals.

Answer: D

3) According to the passage, until recently zoologists believed which of the following about all phocid mothers?

Refer to the lines: "Zoologists had assumed that females of all phocid species, by contrast, use a fasting strategy in which mother phocids, having accumulated large energy stores before they arrive at breeding sites, fast throughout the entire lactation period, which lasts from 4 to 50 days depending on the species."

Answer: E

4) The author of the passage mentions ringed seals most probably in order to

Refer to the line: " In addition, there is already some evidence suggesting that the ringed seal, a phocid species that is similar in size to the harbor seal, may also use a maternal foraging strategy."

Answer: E

This passage is great practice, especially because it is among the most boring things I have ever read.

Full of detail, difficult vocabular about a farily unexiciting topic... a great example of a challenging Gmat RC passage.
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This passage is supremely good at using technical details to distract us. One really important thing to keep in mind on any GMAT RC passage: you don't need any prior knowledge to nail these passages. If you have no idea what a pinniped or a phocid or a otariid is, no problem -- the passage defines them for you.

So let's break down the purpose of each paragraph and avoid getting bogged down in details whenever we can.

Paragraph 1

• There are two kinds of pinnipeds: phocids (let's call them Group P) and otariids (let's call them Group O).
• Group O uses a foraging strategy, while Group P uses a fasting strategy.
• However, recent studies show that harbor seals (which belong to Group P) do forage as well.

What's the purpose of Paragraph 1? To identify how the maternal strategies of Group O and Group P differ, then present the harbor seal as an exception to the strategy of Group P.

Paragraph 2

• Harbor seals from Group P might forage because of their small size and rate of fat store depletion.
• There is evidence to support this explanation.
• The behavior of ringed seals (also in Group P) may also support this explanation

What's the purpose of Paragraph 2? To explain why the harbor seal is an exception (their smaller size and high fat depletion rate), and provide evidence to support this explanation.

Now that we've gotten a handle on the structure and meaning of each paragraph, we see that author wrote this passage to explain how and why harbor seals don't follow the maternal strategies of their group. Let's eliminate answer choices that don't match, and search for the one choice that gets closest to what we've read.


This choice is wrong about why the author is writing the passage (it's not simply to present evidence). It's also wrong about the author's primary focus (it's not several species from Group P that illustrate that group's strategy, but one species from Group P that deviates from that group's strategy). Eliminate (A).


This choice only captures a portion of Paragraph 1. We're looking for the purpose of the passage as a whole. Eliminate (B).


The author never argues that zoologists' understanding of harbors seals' strategy is incorrect. Eliminate (C).


This matches our understanding the passage almost exactly. Paragraph 1 tells us the expected behavior, then informs us that harbor seals' behavior is unexpected. Paragraph 2 presents an explanation (size and rate of fat depletion) for harbor seals' behavior. Let's keep (D) around and see if (E) is any better.


Is the author's main point that the harbor seal belongs to Group O, not Group P? In other words: Did the author write this passage to tell us that we're putting harbor seals in the wrong group? No. We haven't seen any language from the author suggesting that this is the case. In fact, the author consistently refers to harbor seals and even ringed seals as phocids, without ever suggesting that they should be categorized differently.

The author structured this passage to help us understand the maternal strategies of Group O and Group P, then explain why harbor seals use a strategy that doesn't match their group's. This is not the same as telling us that harbor seals belong to a different group altogether. That's why we eliminate (E) and keep (D) as the best answer choice.

I hope this helps you foster a seal -- I mean, foster great reading habits when it comes to identifying the primary purpose!
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Chris/Blog - I have a question in response to #1:

I see where the passage states the lactation periods of PH and OT, but I didn't select that as an answer and hoping for some clarification: The question asks what information the passage INFERS. The passage directly states the lactation periods of both species, so I discarded that answer choice.

IMO the answer is C because the reader can infer that PH and smaller species deplete their fat stores quicker than larger animals.

Thanks
Cody

Yes, the researchers had assumed that all phocid mothers used a fasting strategy, which means that they did not eat at all during the lactation period. The phocid moms did this by acquiring a large amount of fat BEFORE giving birth, and then losing that fat while lactating. AFTER the lactation period, they would be free to forage again and replenish their fat stores.

This is exactly what (E) is telling us:

The researchers believed that phocid mothers built up a lot of fat, lost a large proportion of that fat while lactating and not eating anything, and then replenished their fat stores after the lactation period ended. (E) is the correct answer to question #3.

I hope that helps!
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Passage Map:
P1: Discuss previous belief of the phocid maternal strategies
P2: discuss evidence leading to the belief that phocids are not different from Otariids in terms of maternal foraging

Q1 - Inference
P1 discusses the key differences
A - True. We are told that P has lactation of 4-50 days, and O has lactation of 4months to 3 years
B - not supported
C - not supported
D - Not supported. We are told of phocid depletion in P2.

Q2- Main Idea
A - false. We are told the contrary.
B - No. We are given information supporting the argument that they are not so different.
C - The passage tends to explain moreso than argue against a point here.
D - true. The harbour seals unexpected behaviour is foraging during maternity, explanations are then given in P2.
E - The first part of this is true, but the second part is false.

Q3- Detail
Quite clearly E here.
As found in P1: "mother otariids alternately forage at sea, where they replenish their fat stores, and nurse their young at breeding sites. Zoologists had assumed that females of all phocids species, by contrast, use a fasting strategy"

Implying that fat stores are replenished after fasting.

Q4- Detail
POE through, but the last sentence of P2 gives this away quite easily.
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