http://www.middleschoolscience.com 2009

This PPT was created with the information from the FOSREC Activity “Who’s on First?” and “Fossil Inferences” by UEN.

Sisa atau jejak organisme yang tersimpan dalam batuan setelah materialorganiknya berubah atau hilang.

Petrified - when minerals replace the remains and they become rock

Mold - when the shell remains and the contents dissolve (hollow)

Cast - when the mold becomes filled with minerals that are not a part of the original organism

Unaltered Original Material -

original, unaltered material from

the living organism unaltered bone or shell

Encrustations or entombments –material is trapped inside coating such as amber

Hard body parts such as skeletal bones or exoskeletons

Rapid burial and/or lack of oxygen

Body fossils – actual parts of an organism, unaltered or altered bones, shells, leaf imprints

Trace fossils – evidence of life that is not a body fossil tracks, burrows, casts

Unaltered Original Material -

original, unaltered material from

the living organism unaltered bone

or shell

Encrustations or entombments –material is trapped inside coating such as amber

Unaltered Mummification

-dried material

Replacement – replacement of tissue with minerals

Altered Carbonization – tissue material is decomposed or reduced to a film of carbon

AlteredPermineralization – pores in tissue are filled by minerals

Refrigeration –material is trapped inside ice and tissue is preserved

Mold – reproduction of the inside or outside surface of a living thing

Cast – duplicate of the original organism; usually formed by replacement of inside of living thing

Burrows or borings –

Spaces dug out by living things and preserved as is or filled in

Gastroliths – smooth stones from abdominal cavity of dinosaurs

Coprolites – fossilized excrement; usually preserved by replacement

Tracks – impressions of passage of living things

What is a fossil?The trace or remains of an

organism that lived long ago, most commonly preserved in sedimentary rock

What is a superposition?

Younger rocks lie above older rocks if the layers have not been disturbed

Relative dating: looks at where the fossil is located to determine its age relative to other fossils. This only works if the area has been undisturbed.

Uses radioactive elements near the fossils to determine the actual age of the fossils.

•By determining the age of the radioactive element, scientists can calculate the age of the fossil buried nearby.

The absolute age of fossils is estimated by dating associated igneous rock and lava flows.

The dating of all fossils is included in the Geological Time Scale. This scale divides the time that the earth has existed into 4 eras.

Eras are then divided into periods based on common events in that time period.

Began with the formation of the Earth 4.6 billion years ago.

Bacteria appeared 3.5 billion years ago, followed by algae and fungi.

Cutting of Grand Canyon 2 km/3 m.y. = 1 cm/15 yrUplift of Alps 5 km/10 m.y. = 1 cm/20 yr.Opening of Atlantic 5000 km/180 m.y. = 2.8 cm/yr.Uplift of White Mtns. (N.H.) Granites 8 km/150 m.y. = 1 cm/190 yr.

Movement of San Andreas Fault 5 cm/yr = 7 m/140 yr.Growth of Mt. St. Helens 3 km/30,000 yr = 10 cm/yr.Deposition of Niagara Dolomite 100 m/ 1 m.y.? = 1 cm/100 yr.

35 minutes to birth of Christ 1 hour+ to pyramids 3 hours to retreat of glaciers from

Wisconsin 12 days = 1 million years 2 years to extinction of dinosaurs 14 years to age of Niagara Escarpment 31 years = 1 billion years

Dinosaurs: 150,000,000 yearsRecorded History: 5000 years For every year of recorded history, the

dinosaurs had 30,000 years For every day of recorded history, the

dinosaurs had 82 years For every minute of recorded history, the

dinosaurs had three weeks

What is relative dating?◦ Any method of determining whether an event or

object is older or younger than other events or objects.

What is an index fossil?◦ A fossil that is found in the rock layers of only one

geologic age and is used to establish the age of the rock layers.

◦ Is found in rock layers around the world, ex Trilobites

On your desk, you have 8 large colored index cards with nonsense letters placed on them.

Your task is to determine what the correct sequence of the letters are.

You have two clues:1. The card with the letters “C” and “T” is on

the bottom, or the oldest layer2. Look for a card that has either a “T” or “C”

written on it for the second layer

C T

AGC

UA

NBUNB

ONDXO

MD

This is one possible way to arrange the cards. Questions:

1.What letter is the oldest?2.What letter is the youngest?3.What letter showed up the most?4.Which letters only showed up once?5.Which letters could be index fossils?6.How did you know which was older: “M” or “X”?

Flip your eight index cards over Arrange the index cards that represent

layers of rock and fossils Clues:

1. The oldest layer has the letter “M” in it2. Find a rock layer that has at least one of

the fossils you found in the oldest rock layer

3. Extinction is forever - once an organism disappears from the sequence it cannot reappear later

Teacher Note: I replaced the letters with nonsense letters b/c spelling the word “organism” was too easy for my 5th graders

What problems did you run into when trying to arrange the fossils into the correct sequence?

Would this have been more difficult if you did not know which layer was the oldest to start the activity?

Which organism is the most complex of all the fossils and why?