Scientists studying the physiology of dinosaurs have long debated

Question

Scientists studying the physiology of dinosaurs have long debated whether dinosaurs were warm- or cold-blooded. Those who suspect they were warm-blooded point out that dinosaur bone is generally fibro-lamellar in nature; because fibro-lamellar bone is formed quickly, the bone fibrils, or filaments, are laid down haphazardly. Consistent with their rapid growth rate, warm-blooded animals, such as birds and mammals, tend to produce fibro-lamellar bone, whereas reptiles, which are slow-growing and cold-blooded, generally produce bone in which fibrils are laid down parallel to each other. Moreover, like the bone of birds and mammals, dinosaur bone tends to be highly vascularized, or filled with blood vessels. These characteristics, first recognized in the 1930’s, were documented in the 1960’s by de Ricqlès, who found  highly vascularized, fibro-lamellar bone  in several groups of dinosaurs. In the 1970’s, Bakker cited these characteristics as evidence for the warm-bloodedness of dinosaurs. Although de Ricqlès urged  caution , arguing for an intermediate type of dinosaur physiology, a generation of paleontologists has come to believe that dinosaur bone is mammalianlike.

In the 1980’s, however, Bakker’s contention began to be questioned, as a number of scientists found growth rings in the bones of various dinosaurs that are much like those in modern reptiles. Bone growth in reptiles is periodic in nature, producing a series of concentric rings in the bone, not unlike the growth rings of a tree. Recently, Chinsamy investigated the bones of two dinosaurs from the early Jurassic period (208-187 million years ago), and found that these bones also had growth rings; however, they were also partially fibro-lamellar in nature. Chinsamy’s work raises a question central to the debate over dinosaur physiology: did dinosaurs form fibro-lamellar bone because of an innately high metabolic rate associated with warm-bloodedness or because of periods of unusually fast growth that occurred under favorable environmental conditions? (Although modern reptiles generally do not form fibro-lamellar bone, juvenile crocodiles raised under optimal environmental conditions do.) This question remains unanswered; indeed, taking all the evidence into account, one cannot make a definitive statement about dinosaur physiology on the basis of dinosaur bone. It may be that dinosaurs had an intermediate pattern of bone structure because their physiology was neither typically reptilian, mammalian, nor avian.   1 
 1. The author of the passage would be most likely to agree that the " caution " (line 29) urged by de Ricqlès regarding claims about dinosaur physiology was

(A) unjustified by the evidence available to de Ricqlès 
(B) unnecessary, given the work done by Bakker and his followers 
(C) indicative of the prevailing scientific opinion at the time 
(D) warranted, given certain subsequent findings of other scientists 
(E) influential in the recent work of Chinsamy

2 
 2. The primary purpose of the passage is to

(A) discuss the influence on other scientists of Bakker's argument concerning the warm-bloodedness of dinosaurs 
(B) provide evidence that supports the claim that dinosaurs were cold-blooded 
(C) challenge the contention that dinosaur bone tissue is innately fibro-lamellar 
(D) evaluate the claim that dinosaur bone tissue provides evidence for the warmbloodedness of dinosaurs 
(E) resolve the disagreement between de Ricqlès and Bakker over the nature of dinosaur physiology

3 
 3. According to the passage, the discovery of growth rings in the bones of certain dinosaurs served to undermine which of the following claims?

(A) That modern reptiles are related to dinosaurs 
(B) That bone growth in dinosaurs was periodic in nature 
(C) That dinosaurs were warm-blooded 
(D) That dinosaurs had an intermediate type of physiology 
(E) That fibro-lamellar bone is the product of a rapid growth rate

4 
 4. The author of the passage mentions bone growth patterns in juvenile crocodiles most likely in order to

(A) provide support for the argument that reptiles are not related to dinosaurs 
(B) undermine the claim that most reptiles are slow-growing 
(C) offer an explanation as to why juvenile crocodiles differ from most modern reptiles 
(D) suggest the juvenile crocodiles have a type of physiology intermediate between-f mammals and that of reptiles 
(E) suggest that the presence of fibro-lamellar bone does not resolve the debate over dinosaur physiology

5 
 5. The passage suggests that, unlike Bakker, de Ricqlès believed which of the following about the highly vascularized, fibro-lamellar bone mentioned in the highlighted text?

(A) It was a type of bone found only in a small group of dinosaurs.
(B) It had characteristics that were inconsistent with a growth rate as rapid as that of mammals.
(C) It did not provide sufficiently compelling evidence for warm-bloodedness in dinosaurs.
(D) It was highly vascularized but not truly fibro-lamellar in nature.
(E) It supported the claim that bone growth in dinosaurs was periodic in nature.

anshul0130 · Answer

VeritasKarishma  - Can you please explain relation of below statement in brackets with whole package ?

(Although modern reptiles generally do not form fibro-lamellar bone, juvenile crocodiles raised under optimal environmental 
conditions do.)

Also, please share your thoughts on how to consider and interpret statements that are kept in between brackets or hyphens in passages.

Thanks,
Anshul P

KarishmaB · Answer

Statements in brackets or hyphens are an aside to the topic at hand. They are related to it though a digression and hence they are put in brackets. 
They may help you understand the context of what is being said a bit better, but are not a part of the immediate topic at hand.

Here, we are discussing dinosaur bones and what they tell us about their physiology. 
The question raised is whether dinosaurs form fibro-lamellar bone because of an innately high metabolic rate associated with warm-bloodedness or because of periods of unusually fast growth that occurred under favorable environmental conditions? (Although modern reptiles generally do not form fibro-lamellar bone, juvenile crocodiles raised under optimal environmental conditions do.)

You might think that why is "periods of unusually fast growth that occurred under favorable environmental conditions" an option? So the author tells us as an aside that some reptiles do form fibro-lamellar bones periods of unusually fast growth that occurred under favorable environmental conditions. That is why this is a possible option.
Then he proceeds to answer the question.

Hence it doesn't break the flow but gives us some desirable information.

jabhatta2 · Answer

Hi  KarishmaB  - for the 4th question - while i agree A through D are wrong - i thought 4E was wrong too

-- The presence of fibro-lamellar bones   does   resolve the debate over dinosaur physiology per my understanding - if dinosaurs have fibro-lamellar bones - dinosaurs were warm blooded

-- The question remain un-answered  in the green  is referring to the fact that the author CANNOT say, if the dinosaurs have fibro-lamellar bones or don't have fibro-lamellar bones to begin with

-- That is why the mordern repiles / juvenile crocodiles was mentioned by the author (mordern repiles DONT HAVE fibro-lamellar bone whereas juvenile crocodiles DO have fibro-lamellar bones) -- so both scenario's are possible

-- We just dont know if dinosaurs are like mordern repiles or like juvenile crocodiles.

KarishmaB · Answer

The question tests your comprehension of all that you have read up to that point.

Were dinosaurs warm- or cold-blooded?

Warm bloodied grow quickly so they have haphazard bone filaments (fibro-lamellar) (birds & mammals). Dinosaurs have such bones. 
Reptiles grow slowly so they have parallel laid bone filaments (reptiles). They are cold blooded.

But growth rings were found in dinosaur. Growth rings are found in reptiles showing periods of growth. 
So scientists wondered whether fibro-lamellar bones were because of warm blooded dinosaurs or because of periods of high growth rate (in which case dinosaurs could have been cold blooded).

Now here is the question that came to my mind - reptiles have growth rings but they do not have fibro-lamellar bones. Then why should growth rings in dinosaurs explain fibro-lamellar bones? Growth rings (periods of high growth) does not lead to fibro-lamellar bones in reptiles. Then how can growth rings explain fibro-lamellar bones in dinosaurs?

This is what the author tried to explain by pointing out - (Although modern reptiles generally do not form fibro-lamellar bone, juvenile crocodiles raised under optimal environmental conditions do.)

He explains that periods of high growth (which give growth rings) could lead to formation of fibro-lamellar bones as they do in juvenile crocodiles. He says that is why growth rings could indicate that dinosaurs were cold bloodied.

So he mentions juvenile crocodiles to explain why the presence of fibro-lamellar bone does not resolve the debate over dinosaur physiology. Why we cannot say that dinosaurs must be warm bloodied. Because fibro-lamellar bones are found in juvenile crocodiles (cold blooded) raised under right conditions too.

jabhatta2 · Answer

Hi  KarishmaB  - Per the yellow - you mention juvenile crocodiles are cold blooded

Where in the passage is it mentioned THAT juvenile crocodiles are cold blooded ?

Isn't that using outside knowledge ?

I dont think the RC Passage mentions juvenile crocodiles are cold blooded or warm blooded.

I see the RC passage mentions 'mordern reptiles' are cold blooded (but these mordern reptile DONT HAVE fibro-lamellar bone neither), so i dont think one can assume that juvenile crocodiles MUST BE cold blooded as well

KarishmaB · Answer

We are given: Although modern reptiles generally do not form fibro-lamellar bone, juvenile crocodiles raised under optimal environmental conditions do.

The contrast shows that juvenile crocodiles belong to the group "modern reptiles". Modern reptiles are cold bloodied. We know that crocodiles are reptiles and juvenile crocodiles are just young crocodiles. If crocodiles are cold bloodied, young crocodiles are automatically cold bloodied. An animal cannot change its basic physiology as it grows up.

There is no outside knowledge used here. As you mentioned, no other option makes any sense either. Answers will not be given in the passage in black and white. You will need to derive them from various data bits given all over. 
Also note that this is a GMAT Prep question. GMAT expects you to derive these implications.

agrasan · Answer

Hi experts  KarishmaB   GMATNinja   MartyMurray

In question-1, I understand why option D is correct but wanted to check my reasoning to eliminate option E properly.

My reasoning is: de Ricqls did mention that  "intermediate physiology"  is possible but passage doesn't indicate that Chinsamy's work went towards the intermediate physiology. He just raised a question as highlighted by the passage -  "did dinosaurs form fibro-lamellar bone because of an innately high metabolic rate associated with warm-bloodedness or because of periods of unusually fast growth that occurred under favorable environmental conditions?"

Thus, we can't say de Ricqls' " caution " was influential in Chinsamy's work as Chinsamy didn't do such work at the first place.

Please let me know if above reasoning is correct or I am faltering somewhere.

bb · Answer

Yes, you are on the right track. 
Nothing in the text says or implies that Chinsamy was motivated by, responded to, or in any other way took direction from de Ricqles. The passage only tells us that:

de Ricqles documented highly vascularized, fibro‐lamellar bone and suggested dinosaurs might be physiologically intermediate. 
 Bakker used those same observations to argue dinosaurs were warm‐blooded. 
 Chinsamy found bones with both growth rings and some fibro‐lamellar structure

anushree01 · Answer

Can someone take a moment to explain me Q5 of this passage
I`m still unable to understand!

egmat · Answer

anushree01

I understand your confusion with this question - it's testing a subtle distinction between how two scientists interpreted the  same evidence .

Key Information Location: 
The answer lies in lines 15-18 of the first paragraph:
- De Ricqlès found highly vascularized, fibro-lamellar bone in dinosaurs
- Bakker cited these characteristics as evidence for warm-bloodedness 
-  "Although de Ricqlès urged caution, arguing for an intermediate type of dinosaur physiology"

The Critical Contrast: 
Both scientists observed the  same  bone characteristics, but:
-  Bakker : This bone type = Evidence of warm-bloodedness
-  De Ricqlès : This bone type = Not enough to conclude warm-bloodedness (urged caution, suggested intermediate physiology)

Why C is Correct: 
"It did not provide sufficiently compelling evidence for warm-bloodedness" perfectly captures de Ricqlès's cautious stance. He found the bone but didn't think it was conclusive proof of warm-bloodedness.

Why Other Options Fail: 
 
 A: De Ricqlès found it in "several groups" (not just a small group) 
 B: No mention of growth rate inconsistency 
 D: He documented it as truly fibro-lamellar 
 E: Growth rings are discussed later, not related to de Ricqlès's view

Strategic Framework for "Author Contrast" Questions: 
  
When you see "unlike X, Y believed..." in RC:
 
 Find where both names appear in the passage 
 Look for contrast words: "although," "however," "but," "unlike" 
 The answer will capture Y's  different interpretation  of the same evidence  
 
  Key Practice Resources:

You can practice similar contrast-based RC questions  here  (you'll find a lot of OG questions) - select Reading Comprehension under Verbal and start with Easy/Medium level to solidify your learning.

I hope this helps. Let me know if you're still struggling with this question or any other one!

Scientists studying the physiology of dinosaurs have long debated

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GMAT Reading Comprehension (RC) Questions

Scientists studying the physiology of dinosaurs have long debated

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards