Food chains show energy transfer between organisms. The size of a food chain can vary, yet there is a limit to the number of
levels that a food chain can reach. Why is there a limit to the number of levels that a food chain can reach?
finiti

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.

that scientist would be robert hooke