What are the tools used to …

(i)By studying their structural design - homologous or anologous .It can give evidences of common ancestor. Forelimbs of humans and wings of birds look different externally. However, their skeletal structure is similar. Thus, their origin is similar, but functions are different. While wings help a bird in flight, the forearm helps human beings in various activities. These structures are called homologous organs.

(ii)By the study of fossils.A million years later, some dinosaurs died at the same place with their bodies getting buried on top of the sedimentary rock. As a result, the mud, containing the dinosaurs, also turned into rock.Now, if that area is excavated deeper, dinosaur and invertebrate fossils can also be found.

(iii)Comparing the DNA of different organisms. All species have the same genetic code. So we can trace some evolutionary relationship among the species.