Final answer:
Zedonks are typically infertile due to hybrid sterility, a postzygotic barrier where the hybrid offspring have underdeveloped or non-functional reproductive organs, and their parent species have differing genetics that prevent normal chromosome pairing during meiosis.
Step-by-step explanation:
Zedonks, which are hybrid animals resulting from the mating of a zebra and a donkey, are typically infertile due to a phenomenon known as hybrid sterility. This condition is one type of postzygotic barrier, which means that it occurs after fertilization when the zygote is formed. Hybrid sterility is when the reproductive organs of the hybrid offspring are not fully developed or functional, leading to sterility. The genetics of the two parent species are different enough that their chromosomes do not pair and segregate normally during meiosis, making the production of viable gametes difficult or impossible.