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. the various kinds of animals and plants that once lived in pennsylvania provides evidence of the environmental changes of early pennsylvania from the a) very good record keeping b) plants preserved as fossils c) animals preserved as fossils d) plant and animals preserved as fossils