Final answer:
A mule is an example of an interspecific hybrid that is typically sterile, therefore unable to produce offspring of its own. The mule, being a cross between a male donkey and a female horse, illustrates the concept of hybrid sterility, a type of postzygotic barrier in reproduction.
Step-by-step explanation:
An example of an interspecific hybrid that does not produce fertile offspring is a mule. Mules are the hybrid offspring of a male donkey (jack) and a female horse (mare). This interspecific hybrid is known for being typically sterile due to the differing number of chromosomes of the two species, resulting in an inability to produce functional gametes.
When it comes to postzygotic barriers, hybrid sterility is a common outcome where hybrid individuals are unable to reproduce offspring of their own. Therefore, mules are a classic example of a postzygotic barrier because they cannot successfully contribute to the gene pool of either parent species. This sterility exemplifies the challenges mixed-species offspring face in terms of reproduction.