1. How do we know that there was life millions of years ago??
FOSSILS:
How do we know that there was life millions of years ago??

2. Introduction Fossils are found all around the world.
Scientists that study fossils are called Palentologists
Fossils give us clues to the past

3. What are fossils? Fossils
The remains or evidence of living things, traces of past life

4. What are fossils? Good Fossil Conditions 1. Objects should be hard:
Bone, teeth, shell, wood (Soft things like flesh, fur and petals don’t make good fossils)

5. What are fossils? Good Fossil Conditions
2. Remains need to be there long enough
sometimes the remains get destroyed before a fossil can form

6. What are fossils? Good Fossil Conditions
3. Quick burial- air will rot remains
keeps air from rotting remains, and animals from ruining them

7. What are fossils?
Fossils can be ruined by:
1. Volcanic Activity

8. What are fossils?
Fossils can be ruined by:
2. Bacterial Rotting

9. What are fossils? Fossils can be ruined by:
3. Crushing by other animals

10. What are fossils?
Fossils can be ruined by:
4. Remains eaten

11. What are fossils? Fossils can be ruined by:
5. Weathering & Wave Action (broken down by nature)

12. Fossil Questions In what type of rock do fossils typically form?
How do remains become fossilized?

13. Fossils

14. How do fossils form? Fossil Formation A. In sedimentary rock
B. Marine animal dies, settles to ocean bottom
C. Remains cover by sediment (body decays)
D. Hard parts protected from air
E. Sediment layers continue to build and compress
F. Erosion uncovers fossil

15. Types of Fossils
Molds
Remains cover with sediment, soft part rots leaving a hollow space

16. Types of Fossils
Casts
Formed when the mold gets filled in with hard sediment

17. Types of Fossils Prints Footprints harden in soft mud
Can tell us how it walked, how big, body shape, skin appearance

18. Types of Fossils Changed Hard Parts
Actual remains preserved & hardened with minerals

19. Types of Fossils Actual Remains
Actual parts of plant or animal is preserved, no rotting
Ex: Freezing, drying, amber, tar

20. Frozen entire wooly mammoths
Extremely dried out mummies
Insects in hardened tree sap
Hot tar pits that have hardened: La Brea, California

21. Finding the Age of Fossils
Relative Dating of Fossils
Younger rocks (top layer) are found on top of older rocks (bottom layer)
“LAW OF SUPERPOSITION”

22. Finding the Age of Fossils
Index Fossils
Fossils that lived during a short period of time
Scientists assume that index fossils of the same type of organism are all nearly the same age.
Can help in aging rock

23. Finding the Age of Fossils
Absolute Dating of Fossils
Use radioactive elements whose length of break down is known
C-14 and U-238

24. Finding the Age of Fossils
Fossil Age Rule
A fossil is the same age as the rock that it’s found in

25. Life on Earth: According to Fossils
What have fossils told us?
Life has existed on Earth for nearly 3 billion years

26. Life on Earth: According to Fossils
What have fossils told us?
Life forms have changed (evolved)

27. Life on Earth: According to Fossils
What have fossils told us?
Simple life began in water, evolved, became terrestrial

28. Life on Earth: According to Fossils
What have fossils told us?
Some organisms have become extinct
Trilobite, Woolly Mammoth, Dinosaurs

29. Life on Earth: According to Fossils
What have fossils told us?
Some life forms have hardly changed
Ex: Cockroaches, snails, snakes

30. Assessment Explain why many animals/plants don’t become fossils?
Many remains are crushed, ruined, eroded, rotted, eaten or burned before they become fossils

31. Assessment What types of objects make the best fossils?
Hard parts- teeth, shells, bones, wood

32. Assessment
Describe where most fossils are formed and how they actually form.
Many fossils form in sedimentary rock that used to be covered by oceans. When organism dies, gets buried by sediment in ocean, soft parts rot, hard parts preserved by sediment

33. Assessment Tell about the difference between a mold and a cast
Mold is hollow space left in sediment when animal rots, cast is when mold gets filled back in with other sediment

34. Assessment Explain how changed hard parts fossils are formed
When actual body parts fill with minerals changing them to a harder substance