Fossils

Collecting fossilized shark's teeth is an easy way to begin collecting fossils. They are often found in abundance on public beaches. The teeth shown here were collected in Castle Hain, North Carolina, and are from the Eocene and Cretaceous divisions.

A. What is a fossil?

1. Fossil is any trace of a once-living organism preserved in rock.

a. naturally preserved evidence of life.

b. provide evidence from the past.

c. help scientists infer how life has changed over time.

d. clues to what past environments were like.

Fossil shrimp (Cretaceous)

Mosasaur skull Oxford University Museum of Natural History.

2. Formation of Fossils

a. fossils form when living things die and are buried by sediments. [usually their soft parts do not fossilize]

b. the sediments slowly harden into rock and preserve the shapes of the organism.

c. sedimentary rock is the type of rock made of hardened sediments.

tube worm cast

Questions1. What is a fossil?

2. How do fossils help scientists?a.

b.

c.

3. How are fossils formed?

4. What kind of rock can we find fossils in?

Questions1. What is a fossil? any trace of a once living

organism peserved in rock.2. How do fossils help scientists?

a. provide evidence from the pastb. help infer how life has changed over timec. clues to what past environments were like

3. How are fossils formed?a. when living things are buried by sedimentsb. sediments slowly harden into rock

4. What kind of rock can we find fossils in? sedimentary

A mosquito and a fly in Balticamber that is between 40 and 60 million years old

3. Preserved remains

a. Fossils in Amber- insect preserved in harden tree sap. Animals without a backbone (invertebrate)

b. Mummification – when an organism dies in dry places such as deserts, they dry out so fast that their soft parts don’t decay (bacteria that feed on dead organisms can’t live without water).

Megalodon and Carcharodontosaurus Teeth. The Charcharodontosaurus tooth was found in the Sahara Desert

B. Kinds of fossils :1. Several processes may

cause fossils to form:

a. Mineral Replacement• Permineralization- process

in which minerals fill in pore spaces of an organisms tissuesex. Clam shell ( the hard outer shell of an arthropod is an exoskeleton)

• Petrification- occurs when an organism’s tissues are completely replaced by minerals

ex. Petrified wood

a cast Fossil shell with the replacement by calcite crystals

Petrified cone of Araucaria sp. from the Jurassic (210 mya) of Patagonia,Argentina

b. Frozen fossils – animals such as the wooly mammoth fall into glaciers, die and preserved often whole. [little or no change to the original animal]

c. Fossils in tar – animal fell into thick pits of oil and tar and were preserved. Ex. La Brea Tar Pits/ saber tooth tiger.

Three mammoth statues are included in the La Brea Tar Pits.

Gas bubble slowly emerging from a smaller tar pit at La Brea Tar Pits.

wooly mammoth

Questions

1. List the process that may cause fossils to form.

a.

b.

c.

2. Explain the process of petrification.

Questions

1. List the process that may cause fossils to form.

a. Mineral replacement

b. Frozen fossils

c. Fossils in tar

2. Explain the process of petrification.

When an organism’s tissues are completely

replaced by minerals.

2. Other Types of fossils

a. Trace fossils- any naturally preserved evidence of an animals activity:

• Fossil tracks/ footprints• Burrows (filled in with

sediment)• Coprolites – are

preserved feces [provides info about the diets and habits of animals]

A fossilized dinosaur footprintat Clayton Lake State Park, New Mexico

Climactichnites, probably trackways from a slug-like animal, from the late Cambrian, central Wisconsin. Ruler in background is 18" long.

Copralite - Dinosaur Dung

Dinosaur swimming tracks

b. Mold is a cavity in the ground or rock where a plant or animal is buried.

c. Cast is an object created when sediments fills a mold and becomes a rock. – A cast shows what the

animal looked like on the outside.

Ex. ammonite

casts

mold

Questions

1. Trace Fossils are naturally preserved ___________ of an animals ________.

2. List two kinds of trace fossils.a.b.

3. Explain the difference between a cast and a mold.

Questions

1. Trace Fossils are naturally preserved evidence of an animals activity.

2. List two kinds of trace fossils.a. Tracks or footprints

b. Burrows filled with sediment

c. Coprolites – preserved feces

3. Explain the difference between a cast and a mold. Mold is the cavity and a cast is the object created when sediments fill a mold.

C. Using Fossils to Interpret the Past

1.Paleontologist – scientist who studies fossils.

2. By examining fossils, scientists can find out what happened in the past.

a. Changes in the environment:

• Fossils of marine organisms have been found on what are now mountains.

Dinosaur eggs

b. Changes in Life• Older rock layers contain

organisms different from those found in younger rock layers

3. Change over time – the fossil record provides evidence about the history and how species changed over time.

Fossil ferns and a lump of coal were both formed from the remains of plants that died many millions of years ago.

D. Geological Time Scale1.Time scale that divides the

earth’s history into distinct intervals of time.

a. Eons

b. Eras

c. Periods

d. Epochs

2. Boundaries or intervals represent major changes on earth. a. appearance and disappearance of animals and plants b. changes in global climate c. changes of rock types.

Question

1. What information can we learn from the geologic time scale?

Question

1. What information can we learn from the geologic time scale?

Scale that provides information on earth’s history

a. appearance and disappearance of life forms

b. changes in global climate

c. changes in rock types.