September 2014 LSAT Section 4 Question 15

Hine's emerald dragonflies are an endangered species that live in wetlands. The larvae of these dragonflies can survi...

xDaltonLaney on October 22, 2019

Why is E incorrect?

I was tricked by E because to me that implied they have other sources of food they eat and thus when they eat the dragon flies it helps balance out the ecosystem for the good. Why is this incorrect?

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SamA on October 22, 2019

Hello @xDaltonLaney,

E demonstrates that the crayfish do not totally depend on the dragonfly larvae as a food source. However, it is a bit of a stretch to assume that this balances the ecosystem. Try to stick with the information given in the passage. Also, notice that E says "if the local population of Hine's emerald dragonflies dies out." We are trying to explain why dragonfly populations are healthier where they coexist with crayfish. A condition that occurs when the dragonflies are all dead doesn't explain this.

A is a better choice because it shows how the crayfish, though predators, also have a positive effect on dragonfly populations. They dig chambers filled with water, thus creating more habitat in which the larvae can survive.