Scientists study the fossil records of extinct organisms and compare them with modern organisms to identify similarities and differences. By examining the preserved remains of ancient organisms, researchers can infer evolutionary relationships. For example, the Archaeopteryx, shown above as a fossil and as a model created from the fossil, exhibits both bird and reptile characteristics.
Archaeopteryx has bird-like characteristics such as
, and reptile characteristics such as . This the evolutionary link between dinosaurs and modern birds.