Question

why does gametic isolation not result in a zygote? because their reproductive parts do not fit together making mating impossible because the organisms are not active at the same time and never see each other because the sperm of one species is unable to fertilize the egg of the other species

Explanation:

Gametic isolation is a pre - zygotic reproductive barrier. In gametic isolation, even if the gametes (sperm and egg) of two different species come into contact, the sperm of one species is unable to fertilize the egg of the other species. This can be due to biochemical incompatibilities (e.g., the sperm may not be able to penetrate the egg's membrane because of differences in surface proteins).

Answer:

because the sperm of one species is unable to fertilize the egg of the other species