Which theory ties the fields of biology and geology together?

EVOLUTION

Evolution is considered as the change of characteristics of a species over several generations and depends on the process of natural selection. This is based on the idea that species change gradually over time. This can also rely on the genetic variation which can affect the physical characters of the species. Evidences of this biological processes and changes are proved by geological explorations and researches. Some of evidences proved that other organisms has an advantage over the others.