Transitional+Forms+in+Evolution

Transitional Forms in Evolution

Transitional forms provide the missing links in  certain evolutionary pathways. Modern vertebrates, for example, appear to have evolved first as jawless fish, then bony fish, then amphibians, reptiles, birds and finally mammals. For many groups of organisms there are large gaps in the fossil record because no transitional forms have been found. However, this cannot be taken as proof that the fossils of transitional forms do not exist. It is possible that: • fossils may be out there undiscovered • fossils may have been found but have not been recognised as important • the transitional forms may have developed in a population and an area too small or inhospitable for fossils to develop. This is possible as speciation is most likely to occur in a small, isolated population with a changing environment.