 Petrified Fossils  Molds and Casts  Carbon Films  Preserved Remains  Trace Fossils

Petrified Fossils - How do they form? Mineral rich water soaks into cracks and crevices Minerals “precipitate” and fill the spaces Mineral replace the solid material of an organism

Molds and Casts How do they form? A shell or other structure is buried in sediment and then dissolved by water Mold reflects the shape and surface markings Cast fossils form when the hollow spaces of a mold are filled with minerals

Carbon Films How do they form? Organism is buried under fine sediment Pressure squeezes out liquids and gases, leaving behind a thin film of carbon Show fine details of the organisms structure

Preserved Remains How do they form? Frozen in permafrost Preserved in amber Preserved in tar

Trace Fossils How do they form? Tracks left in soft sediments that later harden Burrows made by animals in sediment, wood or rock that later fill with minerals Fossils of dung and stomach contents

Conditions for Fossilization 1.Rapid burial 2. Possession of hard parts

History of Life on Earth Fossil Succession - each layer has a distinct set of fossils; progress in a definite order

Theory of Evolution – life changes over time from simpler to more complex organisms Natural Selection: individuals that are better adapted to the environment are more likely to survive and reproduce Adaptations: traits that affect an organisms ability to survive

Interpreting the Fossil Record  Correlate rock layers Index fossils – geographically widespread and abundant; existed for a limited time Groups of fossils to establish relative age  Reconstruct past environments Use adaptations of fossils to get clues about the environment they lived in