Aseries of radiographic images taken of the stomach and duodenum after the contrast agent barium has been swallowed is a(n)

A series of radiographic images taken of the stomach and duodenum after the contrast agent barium has been swallowed is an upper GI series, where 
GI stands for "gastrointestinal," which means "stomach and intestines".
This x-ray examination of the upper gastrointestinal (GI) tract,can diagnose problems in your upper GI tract, how to prepare for the procedure, and what to expect afterwards.

It is evolution, because we all have some of the same traits like eye color or shape or ears.