What term describes structures in different species that are similar due to common ancestry?

Structures in different species that are similar because of common ancestry are called homologous structures. They may perform different jobs today, but they retain a shared underlying pattern inherited from an ancestral structure.

The forelimbs of humans, bats, birds, whales, and cats are a classic example. A human arm, a bat wing, and a whale flipper have different functions, yet their bones correspond because they descended from the forelimb of an ancestral tetrapod. Evolution modified the same basic framework in different lineages.

Homologous structures are often confused with analogous structures. Analogous structures may serve similar functions but evolved independently, such as the wings of birds and insects. Vestigial structures are different again: they are reduced remnants whose original functions have been diminished or lost. The concept of homology also applies beyond anatomy; genes and DNA sequences can be homologous when they descend from a shared ancestral sequence.