The term that describes parts of organisms that have a similar function but not structure is analogous structures.

Here's a breakdown:

* Analogous Structures: These are structures that have evolved independently in different species to perform similar functions. They have different evolutionary origins and may look very different.

* Example: The wings of a bird and the wings of a butterfly both allow for flight but have very different structural origins.

This is in contrast to homologous structures, which have similar structures but may have different functions. Homologous structures provide evidence of common ancestry.

Let me know if you'd like more examples or explanations!