Final answer:
Homologous structures are physical features shared among species that have a common ancestor, such as the arrangement of bones in the forelimb, indicating a shared evolutionary history.
Step-by-step explanation:
Structural similarities shared by a wide array of distantly-related species that are inherited from a remote ancestor, such as the number of bones in the forelimb, are termed homologous structures. These structures can be found in different species, displaying a similar pattern of bones that was passed down from a common ancestor. Despite having different functions now, such as the wings of bats and birds, or the hands in humans and the paws in dogs, these structures indicate a shared evolutionary past due to their complexity and similar arrangement. Contrasting with homologous structures, analogous structures are similar in unrelated species because they have evolved to perform the same job, not because they share a common ancestry. An example would be the wings of insects and birds, which look similar and serve the same function of flight, but arose from different evolutionary paths.