Chapter 8 - Fossils What Do Fossils Show About Earth’s History? How Are Fossils Like Today’s Living Things?

What are Fossils? Fossils are the remains of living things. Rocks are not the remains of living things. The oldest rocks are about 4.53 billion years old, nearly a BILLION years older than the evidence of the oldest living things on Earth.

Lesson 1 – What do fossils show about Earth’s history? Approximately 4.5 billion years old Formed from a giant cloud of gas and dust Rocks from space pounded Earth’s surface The outer layer of Earth hardened and formed the crust Volcanoes spewed lava, ash, and gases all over the planet The atmosphere contained no oxygen Oceans started to form About 3.5 billion years ago, single celled organisms appeared and reproduced by dividing Over millions of years, other organisms developed – these organisms no longer exist FOSSILS give us the clues about these early organisms

Fossils are the preserved remains of a living thing.

Fossil Records PROVE that Earth’s crust has moved over time Fossil Records PROVE that Earth’s crust has moved over time. Continental Drift has been taking place for millions of years. As the crust moved from the original Pangea (one GIANT continent), the seven continents we know today formed. They gradually moved into their current position.

Inquiry Question – Why would fossils be found in sedimentary rocks more often than in metamorphic or igneous rocks? Explain.

Fossil Formation Most organisms decay very quickly when they die. However some become buried in sediment, ice, or tree sap. These remains MAY become fossils. Fossils are formed in several ways: Petrified Mold Cast Amber (tree sap) Ice Trace fossils – evidence of an animal’s activities like tracks or burrows Carbon film – a thin coating of carbon that forms when heat and pressure force out most of the remains of a buried organism – the thin coating shows at least part of the organism in great detail Trace Fossils Carbon Film Fossil

Petrified Molds and Casts Ice Amber Water with dissolved minerals seep into the remains of an organism that has died. The minerals replace the soft parts of the organism and harden into a rocklike fossil. Example: Petrified wood The remains of an organism that has died is buried in sediment. The hard parts of the organism do not decay quickly (bones). The sediment eventually hardens into rock and eventually the bones decay. A MOLD is the hollow space left when the hard part finally dissolves. A CAST forms when dissolved minerals fill the space and harden into an exact copy of the decayed organism. FOSSIL FORMATION Ice Mammoths have been buried in ice and snow and their bodies have been preserved because they have not been exposed to air while being frozen. Amber Insects, spiders, and lizards have been trapped in tree sap. The tree sap hardens into AMBER. Amber is now used in expensive jewelry.

Inquiry Question – Why do you think fewer plants than animals became fossils? Which kind of fossil gives scientists the most information about an organism and its environment? Why?

Fossils Found Within the United States https://www.fossilera.com/pages/state-fossils

Lesson 2 – How Are Fossils Like Today’s Living Things? Paleontology is the study of ancient life through analysis of plant and animal fossils. They study ancient life, trying to discover its connection to current life forms on Earth. They try to develop an understanding of the ancient forms’ interrelationship with their environment. Using index fossils and other information about the rocks in which fossils occur, paleontologists aid petroleum geologists in their search for oil and gas.

Fossils and Modern Plants and Animals