Which of these sentences is true with respect to species?

two organisms belong to the same species even if they are separated by a geographical barrier, as long as they can mate and produce sterile offspring.

two organisms belong to the same species even if they are separated by a geographical barrier, as long as they can mate and produce fertile offspring.

two organisms belong to different species if they are separated by a geographical barrier, even if they can reproduce and produce fertile offspring.

"a scientist studying a whale and its surroundings would need to understand the structure of atoms in case something was negatively affecting the whale or its surroundings."

explanation:

this was from the link provided:

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.