In ecologically similar habitats it can sometimes happen that apparently similar organisms arise. These organisms may be entirely unrelated, their similarities coming about as a result of the same selective pressures being applied to each set of organisms. These selective pressures may produce similar structures in unrelated species, for example the wings of all flying animals are very similar because the same laws of aerodynamics apply governing what makes an efficient shape for a wing, irrespective of the animal involved or the physical location. With species of plants which share the same pollinators it can be seen that analogous structures and methods of attracting the pollinating species to the plant are similar, this is because the plants are operating under the same set of selective pressures.

Convergent evolution creates problems for those using evolutionary patterns to try to answer questions relating to taxonomy, in particular to those studying cladistics. It can provide evidence of false relationships and incorrect evolutionary pathways.

Convergent evolution is sometimes called convergence.