[1] In 1995, the reintroduction of gray wolves to Yellowstone National Park initiated a dramatic ecological transformation known as a trophic cascade. [2] Decades of wolf absence had allowed the elk population to explode, leading to severe overgrazing of willow and aspen trees along riverbanks. [3] Once the wolves returned, their predation and presence forced the elk to avoid open valleys, where they were vulnerable. [4] Consequently, the streamside vegetation began to recover rapidly, stabilizing the soil and reducing erosion. [5] This regrowth of trees attracted songbirds and beavers, who used the wood to build dams, creating habitats for fish, amphibians, and waterfowl. [6] The wolves' return ultimately reshaped not just the animal populations, but the physical geography of the park itself.
At this point, the writer is considering adding the following sentence:
'Beavers are known for their ability to significantly alter river ecosystems by building complex lodges and dams.'
Should the writer make this addition after Sentence 4?
- AYes, because it establishes a transition between the recovery of streamside vegetation in Sentence 4 and the return of other animal species in Sentence 5.
- BYes, because it provides essential background information explaining how beaver dams physically reshape waterways.
- No, because it interrupts the paragraph's detailed tracing of the trophic cascade with a general statement that is redundant with the information in Sentence 5.Answer
- DNo, because it introduces a discussion of river ecosystems that is irrelevant to a paragraph focused exclusively on wolf behavior.