#19 - Concept Reference, Must Be True

[Administrator]

Complete Question Explanation

The correct answer choice is (D).

Answer choice (A):

Answer choice (B):

Answer choice (C):

Answer choice (D): This is the correct answer choice.

Answer choice (E):

This explanation is still in progress. Please post any questions below!

[est15]

This was my thought process for #19:

A. Eliminate because you can't compare grasslands to forests since the very first sentence of the passage says that the latitudinal gradient is for same habitat types.

B. This was the answer I picked, though I'm not sure why it's incorrect. I thought if the second passage said "tropical regions, which, unlike the temperate and arctic zones, have been unaffected by a succession of ice ages," it meant that temperate zones HAVE been affected by a succession of ice ages.

C. Eliminate because third passage says "high biomass can exist with few species."

D. Eliminate because second passage says "ice ages have caused less disruption in some temperate regions than in others and have not interrupted arctic conditions." So if arctic conditions were not interrupted but temperate ones were, then the time theory hypothesis suggests that arctic grasslands should have more diverse species than temperate grasslands.

E. Would have been my second choice. It seems like the last paragraph supports this statement. I couldn't find anything wrong with this.

Could you explain why B and E are incorrect and D is correct? I believe my thinking for A and C are correct, but if not, please also let me know the right thought process for eliminating those two answers. Thank you for your help!

[Lucas Moreau]

Hello, est15,

E is wrong because there's a difference between "likely" and "more likely". The regional speciation hypothesis says that tropical and temperate zones are more likely than arctic zones to develop new species, but does not say they are straight up likely. If the arctic zones have a 1% chance and the tropical zones have a 2% chance, neither of them is very likely, lol.

B is wrong because, again, a difference of degree. You are correct in that the second passage means that temperate zones have been affected, but not necessarily "severely interrupted".

D is the best because while the passage argues about why the latitudinal gradient exists, the fact that it exists is not in dispute. So the idea of there being more species in the temperate zone than the arctic zone is the most strongly supported.

Hope that helps,
Lucas Moreau

[est15]

Thank you for your explanation. I forgot to mention that I didn't pick D because it seemed like I had to bring in outside knowledge that the temperate zone is below the arctic zone. I don't think that the passage ever mentioned this. Is this knowledge that LSAC expects us to know and apply on the the LSAT? From past preptests I've done, it seemed as if the answers stayed within the realm of the passage and I never had to rely that much on bringing in outside knowledge.

[Nikki Siclunov]

Hi,

Adding to the comments made earlier - yes, you can assume that temperate zones are closer to the equator than arctic zones are, and that tropical zones are even closer to it. This is not "outside information" as much as a commonly known fact, which anyone is expected to know. Furthermore, the author clearly assumed this to be true when discussing the implications of the latitudinal gradient.

Thanks!

[hannahelbundy@gmail.com]

Will you please help me understand why E is wrong? I chose it because it's relatively close to the equator, which I assumed meant that it too could be explained by rate of speciation.

[Jeff Wren]

Hi hannahelbundy,

First, I want to make sure that you didn't confuse "temperate-zones" with "tropic zones." Tropic zones are the ones that are closest to the equator. Temperate zones are in the middle between the tropics and the arctic. This question is asking about "temperate-zone grasslands."

Answer E is tricky and plays on a common mistake between a comparative statement versus an absolute statement.

Answer E states that if populations are isolated, they are "likely" to adapt and become new species.

In order to check this answer, we should compare this statement to the relevant lines in the passage. The relevant discussion comes at the very end of the passage (lines 55-61). The final sentence compares subgroups in the arctic to subgroups in the tropics and states that subgroups in the tropics (i.e. "the latter") are "more likely" (line 59) to survive and adapt than the subgroups in the arctic.

All that means is that is that the subgroups in the tropics have a better chance to survive and adapt than in the arctic, not that they are are "likely" (i.e. more than 50% probability) to do so. Further, this comparison is between the tropics and the arctic, while the question is about temperate-zone grasslands, which would actually be somewhere between the tropics and the arctic in terms of latitude.

Answer D, the correct answer, is directly supported by the first paragraph of the passage, which states that "the overall number of species increases from pole to equator" (lines 3-4). Since temperate-zone grasslands are closer to the equator than the arctic (i.e. the poles), they would have a higher number of species.