Q7 - Two different dates have been

[alex.chasan]

Having some trouble with this one. . . it seems to me that the only answer that's at all provable based on the text is (D) cold-adapted beetles died out toward the end of the ice age. Wouldn't that have to be true if one of the ways they date the end of the ice age is when warmth-adapted beetles replaced cold-adapted beetles?

Yet, the answer is (E). It seems like you need at least a few more assumptions to justify (E).

Oy, I must be missing something here. . .

[ManhattanPrepLSAT1]

I totally see your position. I just sat here looking at for 10 minutes

This question is a bit tough, but I don't think it's meant to be. There are four statements.

1. there are two dates for the end of the last ice age
2. first date is when warmth-adapted beetles replaced cold adapted beetles
3. second date is when spruces replaced ice masses
4. 1st date is 500 years earlier than the second date

Your answer choice (D) stems from the second statement. Answer choice (E) stems from all four statements. I believe they intended this question to be "draw the conclusion" rather than "find something inferable." Which technically, there should be much of a difference. Regardless, answer choice (D) can be dismissed using the "find something inferable" approach because we know that warmth-adapted beetles replaced cold-adapted beetles in many areas, but that doesn't mean that they died off everywhere - and that's what answer choice (D) implies.

(A) is not true. Warmth-adapted beetles did not cease to inhabit areas where spruces grew. In fact, they thrived in areas covered with spruces.
(B) is not true. The pollen grains did not appear for 500 years after the disappearance of the cold-adapted beetle.
(C) is totally absurd. We know nothing about what happened with the ice masses.
(D) is not necessarily true. We know that the cold-adapted beetles were replaced by warmth-adapted beetles. But we don't know this is true everywhere, so we cannot say they died out.
(E) utilizes all four statements and seems to weave them together well. We do know that the beetles arrived before the spruces, which is what this answer choice states.

[ginsburgb]

I also chose D, and I see why it is incorrect now - thanks for the helpful explanation. But, I'm still having trouble with E. Are we suppossed to assume that soil changes and seed dispersion are part of establishing new spruce forests? It seemed like a jump to me.

[ManhattanPrepLSAT1]

Ahh! Good question. It's not assumed, it's stated. That's exactly what answer choice (E) is saying. Answer choice (E) talks about the rate at which seed dispersion established new spruce forests. According to answer choice (E), that rate is slower than the rate that warmth adapted open-ground beetles colonized the new terrain opened to them.

Just a slight misread...

[ccalice21]

I still have trouble grasping E.

However, if I read the "faster" in E as "earlier", it would totally make sense, but I don't quite get your "rate" interpretation.

Does the rate warm beetles replaced cold beetles have to be faster than the rate spruce forest replaced ice mass just because the first replacement took place in history hundreds of years earlier than the second replacement?

Thanks for any help, I am lost in this argument.

[ManhattanPrepLSAT1]

In this case "earlier" would mean "faster" and vice versa.

Suppose you have two trains departing from a train station at the same time and heading to the same destination. Suppose one of those trains gets there 22 hours after departing and the other train arrives 36 hours after departing. You could say that the first train, both arrived earlier and that it traveled the distance faster. The reason is that they both had the same starting time.

For this question, it's not very precise but essentially the beginning for both issues is the same - the end of the ice-age.

Does that make sense?

[chike_eze]

In this case "earlier" would mean "faster" and vice versa.

Suppose you have two trains departing from a train station at the same time and heading to the same destination. Suppose one of those trains gets there 22 hours after departing and the other train arrives 36 hours after departing. You could say that the first train, both arrived earlier and that it traveled the distance faster. The reason is that they both had the same starting time.

Interesting analogy. This sounds very much like a GMAT Quant (Rate) problem. Nice

[americano1990]

Funny how (D) seems so attractive during review.

It was something you would easily eliminate in the actual testing condition but takes awhile to get it around ur mind.

Like some posters said above, I think (D) is actually inferable from the stimulus. We are told that the study used samples of sediments in order to determine when Warm Beetles replaced Cold Beetles (which actually resulted in the first of the two dates marking the end of the ice age). So i think (D) is something that is definitely supported by the passage.

BUT, the reason why it is wrong can be found in the question stem. We are told not only to find something that is MOST STRONGLY SUPPORTED but also that can serve as a conclusion---> Hence, MOST STRONGLY SUPPORTED CONCLUSION.

If the word CONCLUSION were not in the stem, I would call this a highly debatable question. But thankfully, the specification allows us to eliminate (D). You can test it by applying the THEREFORE test. Read whatever you are told in the stimulus, then say THEREFORE, and then read (D) and (E) respectively. The winner should be clear.

Basically, in the stimulus, you are told about beetle replacement and plant growth. And while (D) focuses only on the former (E) gives weight to both. Its basically like the main point Questions in RC. There may be answers that are correct in terms of the content but too narrow in scope. (D) is one great example of that.

Hope this helps.

[mlbrandow]

I feel like this question definitely rests on proper interpretation of faster as "earlier in time" rather than "quicker rate of change."

Just because there is some approximate end to an ice age doesn't mean there must be a definitive start, or that this start must be mutual among beetles and spruce forests. It's quite possible that the time for beetle change spanned the previous 1,000 years, whereas the time for spruce forest changes spanned only the previous 100 years.

This is a good answer choice if you interpret it as the former, and a terrible answer choice if you interpret it as the latter. There is no support at all for the rate of change of either, only end points.

I suppose, though, one could consider arguing in favor of an answer choice that has a 50% success rate, depending on interpretation, rather than the four other answer choices which are plainly unsupported.

I gaffed on this question, but I'll be sure to keep ambiguity of terms in mind when PTing in the future in case something like this comes up again!

[nflamel69]

The thing that seems awfully out of scope for me on this question on answer D is that it says the one that inhabit the areas covered by ice masses died out. what about the one that inhabited somewhere else?

[agersh144]

I agree with above posters if faster means earlier then it makes sense but if it means rate that seems very questionable & unsupported from the stimulus. Can someone explain the difference?

[ManhattanPrepLSAT1]

In this case it means earlier and it is supported by the stimulus. Think about it as a race. Once the ice-melted, who got there faster (earlier)? The beetles or the spruces?

[agersh144]

Got it that makes sense -- thanks sherm.

[mjacob0511]

I was between (E) and (D) and went with (E) being that it's much more in line with the style of inference questions by tying together the stimulus.

I was worried about (E) because of the "soil changes and seed dispersion" but I thought there was something more wrong about (D). I see that above the emphasis has been on the dying out of the "species" as opposed to just the one's in the arctic.

Someone tell me if I am right please.

(D) says that the cold adapted species died towards the end of the ice age, but according to the passage, the method used to measure the end of the ice age was actually when the warm adapted beetles replaced the cold ones. Maybe the cold one's died a long time before, but it took time until the warm adapted one's really replaced them. For example it could be that out of the 10 million cold adapted one's 9.5 million died in the middle of the ice age and slowly the other .5million began adapting to warmth adaption but that is what took place at the end of the ice age.

In short, we don't know when the cold ones really "died out", only the warm adapted one's replaced them.

[steves]

Ahh! Good question. It's not assumed, it's stated. That's exactly what answer choice (E) is saying. Answer choice (E) talks about the rate at which seed dispersion established new spruce forests. According to answer choice (E), that rate is slower than the rate that warmth adapted open-ground beetles colonized the new terrain opened to them.

Just a slight misread...

Where the passage mentions finding pollen grains in sediment samples, that still seems to require some inference or assumption to get to soil changes and seed dispersion establishing spruce forests (E). I thought less of an assumption was needed to get from replaced = died out (D). But obviously the LSAT folks didn't think so!

[Mab6q]

Regarding D, is it really incorrect because we don't know that all of the arctic beetles died out, or is the issue a matter of what the question was asking for, not an inference but a conclusion?

[TimS316]

Can someone explain why (C) is wrong? Here is my thinking:

Two dates for approximate end of last Ice Age:

1) Warm beetles replaced cold ones
2) Ice masses yielded to spruce forests

1 is 500 years before two.

So this information indicates that at the very least, beetles were probably around before the spruce forests. However, does it not also suggest that the ice masses did not yield to the spruce forests for quite a time after the beetles arrived, maybe even a few hundred years (who knows how long a spruce forest takes to develop)? Does this not indicate that the ice masses were still around after the ice age ended? Several hundred years is a strong claim, but it doesn't seem implausible.

I see the support for E, but C also seems supported by the stimulus. What am I missing?

I rejected (E) because I had this in mind. If the ice masses hadn't yet yielded to the spruce forests, but the beetles were able to colonize, this wouldn't mean they did it faster, it just means they were able to do it sooner.

[JingL911]

Regardless, answer choice (D) can be dismissed using the "find something inferable" approach because we know that warmth-adapted beetles replaced cold-adapted beetles in many areas, but that doesn't mean that they died off everywhere - and that's what answer choice (D) implies.

Thank you for the explanation! But I still felt confused the difference between "in many areas" and "everywhere". Could you point out which parts of the stimulus indicate the scope of "many areas"? Thank you!

[ohthatpatrick]

The basic idea with rejecting (D) is that it doesn't seem like the passage gives us enough info to derive that a certain species went extinct, and saying that "the species died out" is saying it went extinct.

Part of this is assisted by outside knowledge of what ice ages are:
the polar ice caps grow during an ice age, covering much of North America with land ice. As an ice age ends, the glaciers "retreat" back towards the poles, slowly re-exposing the land beneath them.

So for example, glaciers might extend all the way from the North Pole down to New York. As the ice age ends, the southernmost ice will melt first:

so first New York thaws, then New England, then southern Canada, etc.

The scientists here were testing samples of sediments. We're not sure where they were testing, but they would presumably test in areas where there IS ice during an ice age but where there ISN'T ice during a non-ice age.

They wouldn't test somewhere where there's always ice, because that wouldn't give them any way of measuring when an area went from being ice-covered to exposed-land again.

So the idea of "warm beetles REPLACING cold beetles" just means "in that area where we tested".

We could make the same bad, too-strong inference that (D) makes if we said
(D) Toward the end of the last ice age, the areas that were covered by ice masses were eventually all covered by spruce forests

We know that in SOME area, the ice left and a spruce forest emerged, but we don't have enough info to think that there are spruce forests EVERYWHERE that there used to be ice.

Similarly, we know that in SOME area, warm-beetles replaced cold-beetles, but we don't have enough info to think that cold-beetles died out EVERYWHERE.

Since they're "cold-adapted ARCTIC beetles", they presumably could still live in the Arctic. They just can't venture down to the newly exposed New York anymore.

[JeremyK460]

Part of this is assisted by outside knowledge of what ice ages are:
the polar ice caps grow during an ice age, covering much of North America with land ice. As an ice age ends, the glaciers "retreat" back towards the poles, slowly re-exposing the land beneath them.

i hate defending the LSAT and i love all of Patrick's responses, but this isn't a case of needing outside knowledge of ice ages in particular to understand the difference between "swapping" and "expiration" or (to be more specific with ice ages and species relations) "replacement" and "extinction"

i don't know anything specific about ice ages or anything specific about how species relate to them, but i do know that last week i "swapped" my white eggs out with brown eggs...
and not a single person on this thread should be assuming that my white eggs "expired"
because they didn't...
my partner hates them and demanded that i threw them away despite them being brand new

(ashamed to have wasted tho)