Students placed their eggs in vinegar, a mild acid. the egg shells disappeared overnight. based on the passages description of what happened, we could infer that this is a reaction.

I'm pretty sure its a chemical reaction. :)

this protocol provides a detailed procedure for nucleoprotein extraction from cultured cells and tissues in an efficient manner.

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.