The Fossil Record 8-3 8-3

The Fossil Record Fossils – Traces or remains of plants or animals Found in sedimentary rocks

Interpreting the Fossil Record Clues to environmental changes Marine fossils found in desert areas

Fossilization Most animals decompose or are eaten after death. Usually just hard parts of organisms become fossils

Mummification Removal of internal organs Wrapping the body in cloth Dry areas Not much bacteria

Amber Hardened tree sap Insects become trapped and preserved DNA - rare

Tar Seeps Petroleum oozes to the surface Animals become trapped

Freezing Organisms buried in frozen ice or soils do not decay Bacteria cannot survive

Petrification Mineral solutions replace original organic sediment with new material

Imprints Carbonized imprints Partially decays and leaves print behind

Molds and Casts Shells leave empty cavities or molds Sand or mud fills in holes and form casts

Coprolites Fossilized poop Feeding habits

Gastroliths Stones in dinosaurs digestive system

Types of Fossils Trace fossils – fossilized evidence of organisms Footprints

Index Fossils Used to determine relative age of rocks Fossils widespread, abundant, and distinct Lived during a short time span

Index fossils – Absolute Age Rock and fossil can be assumed to be close to the same age