Analyze why the CDC calls hand-washing a
"do-it-yourself" vaccine.

bcoz it prevent many diseseas and skin infection life u have shaked hands with someone who is sick and if u dont wash your hand u can also be sick.

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.