Fossils!Fossils!

What is a fossil? What is a fossil?

Fossils are any Fossils are any evidence such as evidence such as the remains, the remains, imprints, or traces imprints, or traces of once living of once living organisms (plants organisms (plants & animals) & animals) preserved in rocks.preserved in rocks.

Fossils provide clues to past Fossils provide clues to past geologic events and evolution of life geologic events and evolution of life

forms.forms.

PALEONTOLOGISTPALEONTOLOGIST

A Scientist that studies A Scientist that studies fossils to learn about fossils to learn about Earth’s past. Earth’s past. Paleontologists arrange Paleontologists arrange fossils in the order in fossils in the order in which they lived, from which they lived, from earliest to latest. All the earliest to latest. All the information gathered information gathered about past life is called about past life is called the fossil record.the fossil record.

What are the different kinds of What are the different kinds of fossils? fossils?

Original RemainsOriginal Remains Petrified Remains (wood)Petrified Remains (wood) Carbon FilmsCarbon Films Trace FossilsTrace Fossils Molds and CastsMolds and Casts

What is an What is an Original Remain?Original Remain?

Original Remains: Fossils that are the Original Remains: Fossils that are the actualactual bodies or body parts of an bodies or body parts of an organism.organism.

Some processes preserve the Some processes preserve the remains of the organisms with little remains of the organisms with little or no change.or no change.

A. Mummification (drying)-A. Mummification (drying)- Because most bacteria cannot Because most bacteria cannot

survive without water, the survive without water, the mummified organism does not mummified organism does not

decay.decay.

B. Amber- B. Amber- Many insects have Many insects have beenbeen found preserved in found preserved in

hardened resin or sap called hardened resin or sap called amber. amber.

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

D. Ice-D. Ice- Most bacteria cannot survive Most bacteria cannot survive

freezing temperatures, organisms freezing temperatures, organisms buried in frozen soil or ice do not buried in frozen soil or ice do not

decay. The frozen remains of decay. The frozen remains of relatives of elephants called woolly relatives of elephants called woolly

mammoths have been found in mammoths have been found in very cold regions. Freezing has very cold regions. Freezing has

preserved even mammoth’s hair & preserved even mammoth’s hair & skin.skin.

How do organisms become How do organisms become petrified (mineralized)? petrified (mineralized)?

Petrified organisms are fossils in Petrified organisms are fossils in which minerals replace all or part of which minerals replace all or part of

an organism, changing the an organism, changing the organism into stone.organism into stone. The most The most

common organism that common organism that becomes petrified is wood.becomes petrified is wood.

Describe a Carbon FilmDescribe a Carbon Film A thin film of carbon residue that A thin film of carbon residue that forms an outline of the original forms an outline of the original organism leaving behind fine, organism leaving behind fine,

delicate details. delicate details.

When sediment buries an organism, When sediment buries an organism, the weight of the sediment squeezes the weight of the sediment squeezes almost all of the decaying organism almost all of the decaying organism away. Eventually, only a thin film of away. Eventually, only a thin film of

carbon remains.carbon remains.

Hold up a fossil and tilt it back and forth in the light. If it has a shiny, black Hold up a fossil and tilt it back and forth in the light. If it has a shiny, black appearance, then its a “carbon film” fossil.appearance, then its a “carbon film” fossil.

Trace FossilsTrace Fossils

Fossils that contain no Fossils that contain no part of an organism, but part of an organism, but show evidence of their show evidence of their

existenceexistence..

A.A. ImprintsImprints

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

B. CoprolitesB. Coprolites- Fossilized waste - Fossilized waste materialmaterial

a.k.a poop!a.k.a poop!

Casts and MoldsCasts and Molds

Sometimes the molds are filled with sand Sometimes the molds are filled with sand and mud that later hardens forming a and mud that later hardens forming a replica of the original organism. replica of the original organism. These These replicas are called replicas are called castscasts..

A cast is the opposite of a mold.A cast is the opposite of a mold.

Often organisms are buried by sediments. Often organisms are buried by sediments. If the sediments turn into rock and the If the sediments turn into rock and the organisms decay, empty cavities are left organisms decay, empty cavities are left behind. behind. These empty cavities are These empty cavities are called called moldsmolds..

The EndThe End