Scientists who study the structural similarities and differences between organisms are called anatomists.

Here's why:

* Anatomy is the branch of biology that studies the structure of living organisms.

* Comparative anatomy specifically focuses on comparing the structures of different species to understand evolutionary relationships and how organisms adapt to their environment.

While other fields like zoologists and botanists might also study structural features, their focus is broader. Anatomists specifically delve into the details of how organisms are built and how those structures relate to their function.