Final answer:
Mechanical isolation is a premating reproductive barrier that occurs before zygote formation. It prevents reproduction from taking place by not allowing successful mating due to incompatible reproductive structures.
Step-by-step explanation:
Mechanical isolation is a premating reproductive barrier that occurs before zygote formation. It is a type of prezygotic barrier, which means that it prevents reproduction from taking place. Mechanical isolation occurs when closely related organisms try to mate, but their reproductive structures do not fit together. For example, damselfly males and females of different species have differently shaped reproductive organs, preventing successful mating.