Paleontology Fossils and the History of Life on Earth

Fossils Remains or traces of ancient life Bones, Teeth, Shells, Tracks, Trails Soft tissues – rare Preservation is favored by –Hard parts –Rapid burial

How does an organism become a fossil? Rapid burial is essential Protection from scavengers, decomposers, physical deterioration More likely to be preserved if organism has “hard parts”

What conditions favor preservation? Rapid burial is most likely in ocean Many sea creatures have shells So… Marine organisms with shells are most likely to become fossils Other organisms are less easy to preserve. Therefore: Fossil record is biased – many creatures were never preserved

Types of Preservation Original shell, bone or teeth Altered hard tissue (replaced by different minerals) Molds and Casts Trace fossils: burrows, tracks, trails Soft Tissues –Carbon film –Amber –Mummified –Frozen

Original Hard Material

Altered Hard Material

Molds and Casts

Carbon Film

Amber

Impression and Carbon film

Carbon Film - Plants

Utility of Fossils History of Life on Earth Evolution – appearances of new species Extinction – disappearances of species Framework for other events in Earth’s History Guide in exploring for fossil fuels

Mile Markers in Deep Time Periods of time can be recognized by the music of that time Similarly, each interval of Earth History is characterized by a unique set of living creatures

Mile Markers in Deep Time Life is unique for each interval of time because of evolution and extinction Volcanos, earthquakes, mountains, types of rocks repeat throughout history Life does not repeat – it is directional Therefore, we can place other Earth events in a framework based on fossils

Mile Markers in Deep Time The fossil-based framework for Earth history is known as the GEOLOGIC TIME SCALE Units: Eras, Periods, Epochs, Ages

Summary Remains or traces of ancient life Preservation is favored by –Hard parts –Rapid burial Shelled marine organisms are most likely to fossilize Fossil record is biased

Summary Fossils may be preserved as –Original shell, bone or teeth –Altered hard tissue (replaced by different minerals) –Molds and Casts –Trace fossils: burrows, tracks, trails –Soft Tissues Carbon film AmberMummifiedFrozen

Summary Fossils document the history of life on Earth Fossils are proof of evolution and extinction Fossils provide a framework for other events in Earth’s history This framework is the Geologic Time Scale