Q9 - Global Surveys estimate the earth's

[ohthatpatrick]

What does the Question Stem tell us?
Necessary Assumption

Break down the Stimulus:
Conclusion: Leatherback turtle is in danger of extinction.
Evidence: Nesting female leatherback turtles have decreased by more than 2/3 in past 15 years. Any species who decreases by more than 2/3 in 15 years is in danger of extinction.

Any prephrase?
This argument almost seems airtight! "more than 2/3 in 15 years" matches "more than 2/3 in 15 years". "danger of extinction" matches "danger of extinction". Where is the shift?

The rule we're given is that any SPECIES which declines by more than 2/3 is in trouble. Meanwhile, we're told that NESTING FEMALE leatherback turtles have declined by more than 2/3. Is that a species? The conclusion is claiming that leatherback turtles (all of them) are in danger of extinction. So she has made a move from talking about nesting female leatherbacks to talking about the entire leatherback species. A possible objection might be, "Sure the nesting females are in trouble, but all other leatherbacks are doing fine. Thus the SPECIES does not have a 2/3 rate of decreasing." She is assuming that the nesting females are representative of the species.

Correct answer:
A

Answer choice analysis:
A) Yes! Without this assumption, she can't take her fact about nesting female leatherbacks and then apply it to the 2/3 rule about ANY SPECIES.

B) RED FLAG (extreme wording: conditional). The author is only trying to prove that leatherbacks are IN DANGER of extinction. She doesn't need to assume anything about whether the leatherbacks ultimately go extinct. And she certainly hasn't committed herself to this math of "ANOTHER 2/3 in the NEXT 15 years.

C) RED FLAG (extreme wording: roughly the same) This is close to the sampling assumption we wanted. But we don't care if males and females exist in roughly equal numbers.

D) RED FLAG (extreme wording: very few) The author doesn't have to assume anything about whether the turtles live in the wild or in captivity. The rule she is applying doesn't differentiate between wild/captivity. It just says, "if your species declines by more than 2/3, you're in danger of extinction".

E) RED FLAG (extreme wording: the only way) Again, the author doesn't need to assume anything about captive vs. wild turtles.

Takeaway/Pattern: This is a classic Idea Math argument with symbols that repeat twice (2/3 in 15 years … and .. danger of extinction). Usually, arguments with symbol repetition are testing us on whether we can solve for the missing Bridge idea. Here, we needed to reconcile a term shift from talking about NESTING FEMALE turtlebacks to talking about THE TURTLEBACK SPECIES.

#officialexplanation

[peg_city]

Why is B wrong?

Isn't it necessary to draw the conclusion?

What am I missing?

[theaether]

B is a kind of premise booster, just strengthening the premises. It's not an assumption, and it won't fill in the gaps of the original argument. If my argument were something like "if anyone eats too much, they will get fat" then an answer choice similar to B would be "If everyone in town X eats too much, they will end up getting fat." It's not filling in any logical gaps like what if people that eat a lot also exercise a lot, or what if the people are only eating a lot of vegetables and water, etc.

The gap in the argument is a scope shift of "nesting females" falling by 2/3 vs. any species whose "population" declines by 2/3 will become extinct. If nesting females constitute just 1% of the total population, then their decline doesn't mean the total population is declining by 2/3. So we can't jump to the conclusion yet.

We need an assumption like (A). So if the decline in nesting females is proportional to the entire population, that means a 2/3 decline in the females would have to result in a 2/3 decline in the entire population. Now we can go back to the original if-->then statement of, if a population declines by 2/3 it will become extinct.

[WaltGrace1983]

The gap in the argument is a scope shift of "nesting females" falling by 2/3 vs. any species whose "population" declines by 2/3 will become extinct. If nesting females constitute just 1% of the total population, then their decline doesn't mean the total population is declining by 2/3. So we can't jump to the conclusion yet.

Really liked how simple you made that. Here is my explanation. I didn't realize how much I wrote

The population of nesting female leatherback turtles has fallen by more than 2/3rds in the past 15 years
+
Any species whose population declines by more than 2/3rds in 15 years is in grave danger of extinction
-->
The leatherback turtle is in danger of extinction

Question Type: Necessary Assumption

My Thought Process: There is a lot going on here and if you read this too quickly you'll miss it! The overall structure of the argument is simple: this phenomenon is happening (A), if this phenomenon happens than there will be a consequence of extinction (A-->B), thus there will be the consequence of extinction. Pretty simple right? Well yes, it is. However, the real problem with this argument is that it goes from talking about ""nesting female leatherback turtles"" to talking about the consequences of a whole species of ""leatherback turtles."" Look at this! We are taking what could be a tiny sample size and saying that whatever happens to this (perhaps tiny) sample size is indicitave of what is happening to the whole species. Here is baseball analogy for all you fans out there. I say to you ""The Cardinals' ERA for its starters is a whopping 4.53. Any team with an overall ERA of above 4.00 is in trouble and will not make the playoffs. Therefore, the Cardinals will not make the playoffs. This seems like a decent argument. However, here is the problem: we were only talking about starting pitching! What if the starters only pitch for 3-4 innings every game and then the bullpen comes in and is lights out? Can we really say that starting pitchers' ERA is indicative of a team ERA? Well it certainly seems to be generally indicative but in reality we have no idea what the team ERA is. This was a really weird analogy but that is the first thing that came to my head - sports announcers do this kind of stuff all the time. Therefore, what I am looking for in these answer choices is one that solidifies the gap between the ""nesting female leatherback turtles"" (notice...there are TWO qualifications for this group) and the ""leatherback turtles"" in general. I am looking for something that says ""what is true about these female nesting leatherbacks is true for the species in general"""

(A) Correct. This is exactly what I predicted. If it is NOT proportional than perhaps there really is no reason to worry about extinction. This is a tailor-made LSAT answer and it plugs the gap beautifully.

(B) Yea we already know this. This is primarily a premise booster. The premise is word for word saying that "any species whose population declines by more than two-thirds in 15 years is in grave danger of extinction." This answer choice is saying "If the global population of leatherback turtles falls by more than two-thirds over the next 15 years, the species will eventually become extinct." Look at how similiar that is! It really didn't add anything new. It just boosted the premise a bit.

(C) This is by far the most tricky one to eliminate. This answer choice is saying that there are roughly the same amount of males and females. Thus, maybe if the females are decreasing in numbers then the species is declining to dangerous levels. Either way, it doesn't bridge the gap between "nesting female leatherbacks" and "leatherbacks" in general. If we negate this the argument could actually be strengthened. What if the female leatherbacks elicits a much greater number than males? Thus, it doesn't matter that much if the females decrease a lot in number --after all, there are already so many of them! This is one of those tricky answers that, if you don't have a solid understanding of what you are looking for, it could confuse you into thinking that this is the right choice.

(D) Awesome! But who cares? We don’t care if they are in captivity or if they are not! This may in fact strengthen the argument by saying that there is reason to believe that the phenomena of exinction will still occur but we don't need to assume this. If we piggyback off of the analogy I used up there, it would go something like this: "The team, as a whole, doesn't really practice pitching." Something this would certainly strengthen the argument by giving us reason to believe that yea, the Cardinals still won't make the playoffs because it is fairly likely that the bullpen sucks too. However, we don't know anything absolutely. What if the don't need to practice because they are so awesome? This is just like this answer choice. It doesn't matter if they are in captivity or not -- we don't need to assume anything about their living situation

(E) This is very similar to D. Who. Cares? This is virtually an automatic elimination. It doesn't matter what the "only way" to ensure survival is. However, I will say that this would be a better answer choice if there was something about (D) in the actual stimulus. D and E could work well together in a sufficient assumption question. Still though, this answer choice is hardly relevent to what we are dealing with now.

[josh.burgin]

WaltGrace, excellent the way you covered the challenge that option C represents to solving for the correct solution.

[Jonathan.a.schw]

Hi,

I wanted to ask if someone could explain a bit more why C doesn't work. I can see how when it's negated, it still allows to strengthen the argument (for example, if the global population isn't equal of male and female, then the 2/3 female drop could be a tiny portion of a massive or growing male population), but wouldn't it be true that if 2/3 of female turtles disappeared and they're the same number as males, wouldn't that lead to either a drop in males or a low enough number that it would be a 2/3 drop in the total?

Thanks so much.

[Jonathan.a.schw]

Hi,

Just wanted to check in - thank you!