Speciation often occurs over millions of years of evolution. However, a new species can evolve in a single generation. Which of the following events
provides a mechanism for rapid evolution over a single generation?

sheep is a herbivore animal whereas grasshopper belongs to the class chordates but both of them feed on greens.  

if grasshopper and sheep feeding on a pasture land, i do not think both of them will have any impact on each other. however, the number of the species can make difference. since sheep feed on greens, there is a possibility there left no pasture land for the grasshoppers or they may get extinct.

feral cats are estimated to eat tens of millions of native animals each night in australia