Which is an example of a chemical reaction

C6H12O6 (glucose) + O2 (oxygen) -> CO2 (carbon dioxide) + H2O (water) + sunlight energy (ATP). The reaction is called cellular respiration and it is used in plants and animals to break down sugars into usable energy to complete bodily functions.

Explanation:

A chemical reaction is defined as the process in which one or more substances reacts to form one or more products which are chemically transformed means the constituent atoms of the reactants are rearranged unlike physical reactions. No new atoms are  created or destroyed, bonds between the atoms in the reactants are broken and the atoms rearrange themselves and form new bonds to make the product.  For example iron and oxygen combine to form rust, sodium acetate is formed by the combination of vinegar and baking soda etc.

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.