Q6 - Contrary to what many people believe, the number of spe

[ohthatpatrick]

Question Type:
Weaken

Stimulus Breakdown:
Conclusion: The number of species is probably not dwindling.
Evidence: Extinctions are natural. This year we have the same number going extinct as in 1970. But species emergence is also natural. We probably have the same rate of emerging species as we've had for the last several centuries.

Answer Anticipation:
The truth value of the author's conclusion hinges on whether the number of species emerging each year is at least as high as the number of species going extinct each year. We have no precise comment to that effect. Instead, we have two arbitrary benchmarks:
The rate of species going extinct is comparable to 1970's rate.
The rate of species emerging is comparable to that of the last several centuries.

So the author is assuming the rate species have emerged over the last several centuries is at least as great as the rate species went extinct in 1970.

Correct Answer:
A

Answer Choice Analysis:
(A) Ultimately, yes. Since the author uses 1970 as a benchmark year, to make us feel better about the comparative rate of extinction / speciation, this answer weakens by painting an unflattering picture about 1970. In 1970, the number of species on Earth dwindled. So this year provies poor support for an author drawing the opposite conclusion.

(B) Getting specific about regions is out of scope. Our conclusion is about Earth's total number of species.

(C) This doesn't say anything about whether the current rate of losing species is offset by the rate of getting new ones.

(D) "Concern" is out of scope. We need to know the actual numbers.

(E) This shows a difference In detecting endangerment. We need information about the actual number of species going extinct / being created.

Takeaway/Pattern: The conclusion is a very mathematically specific claim, so it behooves us to think about this argument in those terms. Once we pinpoint that we need to quantify how many species we've lost vs. gained, the relevant comparison between 1970 and 'the last few centuries' is clear. However, in the end, the correct answer just attacks one of those benchmarks as sketchy support.

#officialexplanation

[randitect]

I chose C over A because C makes the decrease in number of species explicit. Is the problem with C that the majority could have gone extinct ages ago, and not in the past several centuries?
Although A was a close second, I saw it as weak because it could just be a single exception...one year with a higher rate of species' extinction than emergence.

Advice (ideally before Saturday!!) would great. Thank you.

[1koolkat1]

C is incorrect because it doesn't really weaken the argument even if the statement is true. So what if a majority have gone extinct? The Columnist says this is okay because new species emerge at about the same rate anyway to cover the loss.

A weakens the first premise that many species are likely to go extinct this year as went extinct in 1970 by using the second premise against it-- the loss wasn't covered!

[1koolkat1]

Thought I'd create an account and reply just to help you out. Taking it Saturday as well so good luck to you!

Hope that helps.

[sumukh09]

I don't see why E) is wrong. If scientists are now better able to identify species facing extinction than in 1970 then doesn't that imply that in 1970 the figures may have been understated since scientists were less able to identify species facing extinction and thus unable to provide an accurate measure? Moreover maybe more species were being extinct than emerging in 1970 but scientists did not have the technology or resources to discover this fact and so understated the relative rate between extinct species and emerging species. If they could not provide an accurate measure then that would consequently affect the conclusion that the number of species is not dwindling.

Also I think A) is a terrible answer for the reason mentioned above - so what if there were less species that emerged in 1970 than species that went extinct? It's only one year and if the rate is "about the same" then couldn't there be another year where more new species emerged than went extinct to offset the 1970 relationship? Further the stimulus says "about as many species are likely to go extinct this year as in 1970" and this qualification should seemingly protect the idea that the rate at which species are going extinct and emerging could plausibly have a differential with more species being extinct than emerging for this year.

[fmuirhea]

sumukh09,
There's a slight language shift with (E) that I think makes it incorrect. The evidence is about actual extinction, not the ability to identify species at risk of extinction. Presumably, even if the scientists didn't see the extinction coming in 1970 (i.e., they were less able to identify species at risk), they would still be able to identify when those species actually went extinct. Does the obliviousness of the scientists affect the actual extinction rate?

The chief problem with this argument is that it relies on a comparison between time periods which is vague about the rate of extinction vs. the rate of the emergence of new species. Here's a breakdown of the argument:

P: approximately equal extinction rate now as in 1970
P: approximately equal new species emergence rate now as in past centuries (including 1970)
C: number of species not dwindling, i.e., new species rate > extinction rate

Okay, so both rates are comparable with what they've been in the past, but what were they in the past? The evidence is not specific enough about the relationship between extinction and emergence, so (A) weakens by pointing out that extinction outstripped emergence in 1970, so, since the rates are comparable today, it's likely still outstripping it. Note that you could easily strengthen this argument by pointing out precisely the opposite - that more species emerged in 1970 than went extinct.

[kyuya]

Conclusion: the number of species on earth is probably not dwindling.

Why?

- as many species are likely to go extinct as in 1970.
- BUT.. new species are emerging at about the same rate that they have been for the last several centuries

The assumption here is that in the 1970's new species were coming in at a rate that, in relation to how fast they were becoming extinct, did not leave the population dwindling. However, we are provided NO info about 1970's at all.

(A) Looks good. If this were true, then it would be true that species on earth would indeed be dwindling, destroying the argument.

If we know that there are more lost than gained ( 1970's levels) and this is what is used as a premise in the argument, the premise no longer acts as a support for the conclusion.

(B) This is just irrelevant. Tells us nothing about extinction or reproducing.

(C) Seems like a random fact. Tells us nothing about extinctions or birth rates.

(D) CONCERN tells us nothing about actual numbers.

(E) This is also irrelevant, tells us nothing about new emergence vs extinction.

This is a question where I think if we stick to the core, the wrong answers stick out like a sore thumb .

[phoebster21]

I think a lot of the confusion stems in the way the word "same" is used.

when I first read the last sentence, I took the word "same" to be referring to the rate of extinction. I.e. "new species are emerging at about the same rate," - OKAY, so the emerging rate is about the same as the extinction rate (which would imply no increase or decrease in the CURRENT amount of species on earth)

When i re-read it, i realized the word "same" was referring to the same rate AT that time in the past (or several centuries ago).

The rate today is the SAME as the rate BACK THEN. NOT that the rate of emergence is the same as the rate of extinction.

Then the whole argument just rests on, "okay, well what WAS the rate back then?" (or in 1970).

[jon.sesso]

sumukh09,
There's a slight language shift with (E) that I think makes it incorrect. The evidence is about actual extinction, not the ability to identify species at risk of extinction. Presumably, even if the scientists didn't see the extinction coming in 1970 (i.e., they were less able to identify species at risk), they would still be able to identify when those species actually went extinct. Does the obliviousness of the scientists affect the actual extinction rate?

The chief problem with this argument is that it relies on a comparison between time periods which is vague about the rate of extinction vs. the rate of the emergence of new species. Here's a breakdown of the argument:

P: approximately equal extinction rate now as in 1970
P: approximately equal new species emergence rate now as in past centuries (including 1970)
C: number of species not dwindling, i.e., new species rate > extinction rate

Okay, so both rates are comparable with what they've been in the past, but what were they in the past? The evidence is not specific enough about the relationship between extinction and emergence, so (A) weakens by pointing out that extinction outstripped emergence in 1970, so, since the rates are comparable today, it's likely still outstripping it. Note that you could easily strengthen this argument by pointing out precisely the opposite - that more species emerged in 1970 than went extinct.

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Great explanation! Did not notice the language shift for (E) on the first read. I had narrowed it to A and E. I chose A for two reasons. First, it directly impacts the conclusion by clarifying the premise whereas (E) in fact weakens the 1970 premise as opposed to weakening the conclusion. I have observed that LSAT writers are only able to sleep at night by convincing themselves that nearly all premises in the stimulus are irrefutable. I'll give my take on (E) to add on to the above poster's analysis in a minute, for those interested.

But first I'll further justify (A). This answer choice actually completely obliterates the argument (vs merely "weakening" it). Key word to look for in the stimulus, as previous poster noted, is "rate". Where do we see this word? It's in the second premise, which essentially says that the rate (ratio) or relationship between species going extinct vs new species emerging, has been virtually the same over the last several centuries (Remember: an LSAT premise = religion). So if this ratio is the same now as it has been for the last, say, 200 years, then we can deduce that the ratio is the same now as it was in 1970.

So how do we know that the number of species on Earth is not dwindling (this is the conclusion of the argument)? Well, contrary to what Columnist thinks he's telling us, we don't know because he did not tell us whether the numerator is bigger than the denominator. If, for example, we put the extinct species on top of ratio and emerging species on bottom, then for this conclusion to be valid we need that number on top to be bigger than that number on bottom. But all we know from his argument is that the ratio is the same now as it was in 1970.

Answer choice (A) gives us what we need to destroy this argument. This AC tells us that the ratio of extinct/emerge species was greater than 1; meaning, the conclusion that the number of species on Earth most definitely is shrinking.

Answer choice (E): While I really like what the above poster pointed out about the verbiage "identify species FACING serious risk", I was able to eliminate using common sense logic (as opposed to LSAT logic; I know the two often butt heads but in this case we're safe, thankfully). This explanation I suppose is meant for those who, like me, glossed over that phrase and changed the meaning to, "scientists are better able to identify species that are now extinct."

Even if (E) told us this, it still would be incorrect. It is illogical to infer that the annual rate (extinction/emerging) would be impacted at all because scientists are now better able to identify species that are or that have become extinct. If this is true, the number of species that became extinct in 1970 would still be the same. The number reported, on the other hand, may or may not change. It would increase, if, say, scientists in 1970 missed the extinct circa 1970 8 legged Black Widow Hound (How'd they miss THAT????) that was later identified by scientists circa 2016. Either way, This is irrelevant.

[TillyS471]

this is pretty straightforward.
A attacks the very flaw, which is just because the rate of extinct didnt change, nor did the emergence rate. does not say anything about the rate extinct being more or less than the emergence rate, which is what will constitute to species dwindling or growing ..
B,C,D,E are all very irrelevant. They have nothing to do with the argument's gaps, typically , these answers would be ignored automatically, especially when there is an answer attacking the gap directly.

Weaken and strengthening Qs are sisters, they both find the gap and strengthen fills the gap, weaken attacks the gap.