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 CastsHow 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 FilmsHow 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 FossilsHow 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 EarthFossil 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