Explain the importance of fossils in deciding evolutionary relationships.

Fossils are the dead remains of plants and animals which undergo several physical and chemical processes after they are dead.

Fossils help us in determining how a presently living species evolved or developed from the old species.

Example- Archaeopteryx lithographica is a fossil that resembles a bird (has feathers and wings) but has several features of reptiles (tail and teeth) . So Archaeopteryx is supposed to be the connecting link between aves and reptiles thus suggesting that birds have evolved from reptiles.