PrepTest 154, Section 2, Question 3
Horses, although descended from a forest-dwelling ancestor, thrive(42 more words not shown)
Which one of the following,(18 more words not shown)
- AThe forest-dwelling ancestor(8 more words not shown)
- BThe only true(13 more words not shown)
- CSome modern species(14 more words not shown)
- DDuring cold periods(15 more words not shown)
- ESeveral cycles of(17 more words not shown)
Reading the argument
More horses, then far fewer horses. What could make the population swing that way?
One possibility is food. Imagine a population growing until the horses eat too much of the available vegetation. A food shortage could then reduce their numbers. With fewer horses eating, the vegetation might recover and allow the population to grow again. That's a possible story to investigate, not something the passage has established.
Now add the timing. The latest peak came during a cold period, followed by warming. Why would the horses do especially well in the cold? Maybe cold conditions provided more of their food. Maybe they reduced competition from another animal, such as deer. We aren't given enough to choose a particular explanation yet.
What we’re looking for
The question asks us to explain both the peak and the rapid decline. Keep that whole target in view. A fact that merely tells us horses can survive somewhere cold won't explain why their numbers subsequently fell. I don't have a settled prediction, but I know what a useful answer must connect: the changing conditions and the rise and fall in the horse population.
Working the answers
- A
The ancestor's size doesn't explain this population cycle. Even if those earlier animals were much smaller, we still need to know what changed around the cold period and the warming that followed. A gives us a difference between ancestors and horses, not a reason for the peak and decline.
- B
A modern horse living in cold grasslands makes it easier to imagine horses tolerating cold conditions. But tolerance isn't the whole puzzle. Why did the earlier population grow so large, and why did it then shrink? This fact about a modern type of horse doesn't supply that explanation.
- C
Zebras living in warm grasslands doesn't tell us how the changing climate affected the horses in question. We can't simply transfer a modern relative's habitat to this earlier population. And it still leaves the rise followed by decline unexplained.
- DCorrect
This gives the temperature changes a consequence that matters to horses: changes in their habitat. They thrive in grasslands. During cold periods, extensive grasslands provide more of that habitat, making the population increase understandable. As the climate warms, those grasslands tend to become forest, taking suitable habitat away and helping explain the decline. Both halves of the pattern now fit together.
- E
Repeated changes in temperature aren't an explanation of the horses' response to those changes. We already have a cold period followed by warming in the most recent cycle. Saying that similar cycles happened several times still leaves us asking why the horses increased and then declined. D supplies that missing connection through their habitat.
More Paradox questions
Learn the LSAT our way
Our platform drills Paradox questions at your level and adjusts as you improve.