1. Welcome to Class
How do we determine the age of something?

2. Agenda
Radioactive Decay Lab
Fossils Movie
Fossils Notes

3. Radioactive Decay Lab

4. Movie Fill out the worksheet as you watch the movie
I will be collecting these

5. FOSSILS fossils - trace or remains of organisms that lived long ago
discovered in sedimentary rock
paleontology - scientific study of fossils
Help find relative and absolute ages of rocks

6. Interpreting the Fossil Record
Fossil Record – provides evidence about the history of life on Earth
Shows how organisms have changed over time
Provide clues to past geologic events, climates, and the evolution of living things over time
see how environmental changes affected living organisms

7. Interpreting the Fossil Record
What do these giant fossilized oysters tell us?

8. Fossilization
Dead organisms buried quickly or protected from decay become fossils
Generally only the hard parts become fossils
Rarely an entire organism may be preserved
Sometimes only a replica of the original organism remains
Others provide evidence that life once existed

9. Mummification Mummified remains are found in very dry places
most decay causing bacteria cannot survive in these places
Some ancient civilizations mummified their dead
extracted internal organs and wrapped the body in strips of cloth

10. Amber
Insects get trapped in the sap and are preserved when the sap hardens
Hardened tree sap is called amber
Delicate features (legs/antennae/DNA) can be preserved

11. Tar Seeps
When thick petroleum comes to Earth’s surface, it forms a tar seep
covered by water
Animals become trapped and preserved in the tar

12. Freezing
The low temperatures of frozen soil and ice can protect and preserve organisms
Most bacteria cannot survive freezing temps., organisms buried in frozen soil or ice do not decay

13. Petrification
Mineral solutions (groundwater) replace original organic materials
Some common petrifying minerals are silica, calcite, and pyrite.
The substitution often results in the formation of a nearly perfect mineral replica of the original organism

14. Types of Fossils Using a book, look up types of fossils Include:
trace fossils
imprints
molds and casts
Coprolites
Gastroliths

15. Types of Fossils
trace fossil - a fossilized mark that formed by the movement of an animal on or in soft sediment
No part of the original organism survives in fossil form
fossilized evidence of past animal movement
provide information about prehistoric life
A trace fossils in an important clue to the animal’s appearance and activities.

16. Imprints
Carbonized imprints of leaves, stems, flowers, and fish made in soft mud or clay
When original organic material partially decays, it leaves behind a carbon-rich film
An imprint displays the surface features of the organism

17. Molds and Casts
After a shell is buried, it decays and leaves an empty space called a mold
sand or mud fills a mold and hardens forming a cast
A cast is a replica of the original organism

18. Coprolites
coprolites - fossilized dung or waste materials from animals
They can be cut into thin sections and observed through a microscope.
See the feeding habits of animals, such as dinosaurs

19. Gastroliths
Some dinosaurs had stones in their stomachs to help grind their food
these stones, called gastroliths, survive as fossils
Gastroliths are recognized by smooth, polished surfaces and their close proximity to dinosaurs remains

20. Index Fossils
Index fossil - a fossil used to establish age of rock layers
distinct, abundant, widespread
existed for only a short span of geologic time
Help determine relative and absolute ages of rock layers

21. Index Fossils and Absolute Age
Scientists can use index fossils to estimate absolute ages of specific rock layers
Lived during short spans of geologic time, the layer where an index fossil was discovered can be dated accurately
Scientists can also use index fossils to date rock layers in separate area