Topic: Fossils PSSA: A / S8.D.1.1

Objective: TLW explain what a fossil is and compare different ways living things can be fossilized. TLW explain what a fossil is and compare different ways living things can be fossilized.

Mi #1: What is a Fossil? A fossil is the preserved remains or physical evidence of a living thing. A fossil is the preserved remains or physical evidence of a living thing. Fossils are important for geologists because they provide evidence of what life was like long ago. Fossils are important for geologists because they provide evidence of what life was like long ago.

MI #2: Fossils in Rock The hard parts (bones, teeth, etc.) of organisms that die and are quickly buried in sediments may be preserved in rock. The hard parts (bones, teeth, etc.) of organisms that die and are quickly buried in sediments may be preserved in rock. mogallery.html mogallery.html mogallery.html mogallery.html

MI #3: Fossils in Amber Hardened tree sap from ancient trees is called amber. Hardened tree sap from ancient trees is called amber. Sometimes small organisms (such as insects, lizards, etc.) may be trapped in the sap and preserved. Sometimes small organisms (such as insects, lizards, etc.) may be trapped in the sap and preserved. Amber is unique because the entire organism, soft tissue and all, is preserved. Amber is unique because the entire organism, soft tissue and all, is preserved.

MI #4: Petrifaction Petrifaction is the process by which an organism’s tissues are replaced by minerals. Petrifaction is the process by which an organism’s tissues are replaced by minerals. One type of petrifaction is permineralization, in which the pores in an organism’s hard tissues (bone or wood) are filled with minerals. One type of petrifaction is permineralization, in which the pores in an organism’s hard tissues (bone or wood) are filled with minerals.

MI #5: Asphalt In some places on Earth, asphalt wells to the surface and is covered by a layer of water. In some places on Earth, asphalt wells to the surface and is covered by a layer of water. Organisms that attempted to drink from these pools often became trapped and preserved. Organisms that attempted to drink from these pools often became trapped and preserved. The most famous asphalt fossils are found at the La Brea Tar pits in Los Angeles. The most famous asphalt fossils are found at the La Brea Tar pits in Los Angeles.

MI #6: Frozen Fossils In subfreezing regions of the world (particularly Siberia and Northern Canada) dead organisms may be preserved in ice. In subfreezing regions of the world (particularly Siberia and Northern Canada) dead organisms may be preserved in ice. Numerous mammoths have been discovered this way. Numerous mammoths have been discovered this way.

MI #7: Molds and Casts A mold is a cavity in rock where a plant or animal was buried. A mold is a cavity in rock where a plant or animal was buried. A cast is an object created when sediment fills a mold and hardens into rock. A cast is an object created when sediment fills a mold and hardens into rock. Many ancient shellfish have been fossilized in this way. Many ancient shellfish have been fossilized in this way.

MI #8 Trace Fossils Naturally preserved evidence of animal activity is called a trace fossil. Naturally preserved evidence of animal activity is called a trace fossil. The most well known trace fossils are footprints. The most well known trace fossils are footprints. Burrows of ancient shellfish may fill with sand and harden. Burrows of ancient shellfish may fill with sand and harden. Gastroliths are gizzard stones from sauropod dinosaurs. Gastroliths are gizzard stones from sauropod dinosaurs. Coprolites are fossilized dung. Coprolites are fossilized dung.

Mi #9: Using Fossils to Interpret the Past Fossils record an incomplete history of life on Earth. Fossils record an incomplete history of life on Earth. Fossils give evidence to environmental change. Fossils give evidence to environmental change. Fossils can help geologists determine the age of rock layers. Fossils can help geologists determine the age of rock layers. Index fossils are fossils of organisms that lived during a short well defined geologic time span. Index fossils are fossils of organisms that lived during a short well defined geologic time span.

So What…? Real Life Application Understanding fossils allows geologists to interpret the environment and ecology of prehistoric times. Understanding fossils allows geologists to interpret the environment and ecology of prehistoric times.