Fossils!

Any evidence or remains from an organism that existed long ago FOSSILS Any evidence or remains from an organism that existed long ago

Scientists that study fossils to learn about Earth’s past. PALEONTOLOGIST Scientists that study fossils to learn about Earth’s past.

Fossils provide clues to past geologic and biologic events.

How do fossils form? Fossils form when they are quickly covered in sediments. Usually, only the hard parts of organisms are preserved because the soft parts decay.

The Formation of Fossils Video Clip

What are the different kinds of fossils? Original Remains Petrified Fossils Carbon Films Trace Fossils Molds and Casts

The Types of Fossils and How They Formed Video Clip

Kinds of Fossils Original Remains: Fossils that are the actual bodies or body parts of organisms. Some processes preserve the remains of the organisms with little or no change.

A. Mummification (drying)- Because most bacteria cannot survive without water, the mummified organism does not decay.

B. Amber- Many insects have been found preserved in hardened resin or sap called amber.

C. Tar - Formed by thick petroleum oozing to the Earth’s surface C. Tar - Formed by thick petroleum oozing to the Earth’s surface. The tar beds are often covered with water. Animals that came to drink the water became trapped in the tar and were preserved.

D. Ice- Because most bacteria cannot survive freezing temperatures, organisms buried in frozen soil or ice do not decay. The frozen remains of relatives of elephants called woolly mammoths have been found in very cold regions. Freezing has preserved even mammoth’s hair & skin.

II. Petrified Fossils- It looks like the organism but it is rock II. Petrified Fossils- It looks like the organism but it is rock. They are fossils in which minerals replace all or part of an organism, changing the organism into stone.

III. Carbon Films- A thin film of carbon residue that forms an outline of the original organism. . When sediment buries an organism, the weight of the sediment squeezes almost all of the decaying organism away. Eventually, only a thin film of carbon remains.

IV. Trace Fossils (Traces of Organisms) Fossils that contain no part of an organism, but show evidence of their existence.

Imprints When an outline of an organism is pressed into soft sediment (mud) and the sediment turns into stone preserving the outline, such as the footprint of an animal or the outline of a leaf.

B. Casts and Molds Often organisms are buried by sediments. If the sediments turn into rock and the organisms decay, empty cavities are left behind. These empty cavities are called molds. Sometimes the molds are filled with sand and mud that later hardens forming a replica of the original organism. These replicas are called casts.

Molds

Casts

C. Coprolites- Fossilized waste material

D. Gastroliths- stones swallowed by organisms to help them digest their food.

How are tree rings used to show changes in past life and environment? The width of a tree ring is determined by the amount a tree grows in one year. In a dry year the tree would not grow very much so the ring would be thin. In a year with lots of rainfall a tree would grow a lot and the ring would be thick. By analyzing the width of tree rings scientists are able to predict what weather patterns looked like over time.

Thin ring = little rain and little growth Thick ring = lots of rain and lots of growth

How are ice cores used to show changes in past life and environment? The layers of ice show a vertical timeline of part of Earth’s past. Ice cores help scientists understand how Earth’s climate has changed and might change over time. Air trapped in ice shows how the atmosphere has changed over time Dust or ash in snow may indicate a large volcanic eruption Differences in air content in the ice show temperature changes over time

How Fossils Help Us Learn about the History of the Earth Video Clip

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