Afossil is any natural evidence of prehistoric life that provides some idea of the size, shape, or form of the organism. a fossil does need not to be a whole animal or plant. broken fragments are also fossils, as are the tracks left behind by the organisms. fossils provide important evidence of how life and environmental conditions have changed. the fossils found in rock formations of different time periods differ because the environment on earth has changed. fossils can be used to determine the climate and the environment of early pennsylvania. what evidence can fossils provide to determine changes in an environment? a) plants are preserved as fossils b) animals are preserved as fossils c) fossils cannot be used to determine the history of an environment d) fossils demonstrate how organisms evolve and change in time and environments