When barium hydroxide, ba(oh)2, mixes with water, the solution turns cold.
what is an indicator of a chemical change in the scenario?
formation of a gas
formation of a precipitate
change in energy
change in color

because of

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.

i think that is new experiments yield untrustworthy data and should be carefully considered, because you don't know what will happen with the experiments.