2. Paleontology—The Study of Past Life
• The history of the Earth would be incomplete
without knowledge of the organisms that have
inhabited our planet and the conditions under
which they lived.
• The science involved with the study of past life
is called paleontology.
• Paleontologists study fossils, which are the
remains of organisms preserved by geologic
processes.

3. Fossil
 Preserved remains of a past organism

4. FORMATION OF FOSSILS
 Fossilized- the process of becoming a fossil.
 Fossils are evidence of past life, preserved in
rock.
 Most fossils form when living things die and
are buried by sediments.
 The sediments slowly harden into rock and
preserve the shapes of the organisms.

5. The Fossil Record and life
 The fossil record is the complete body of
fossils that shows how species and ecosystems
change over time.

6. What do fossils tell us?
 Fossils provide evidence of how
life has changed over time.
 Fossils help scientists infer how
Earth’s surface has changed.
 Fossils are clues to what past
environments were like.

8. Types of fossils
 Petrified fossils
 Molds and casts
 Carbon films
 Trace fossils
 Index fossils
 Preserved remains

9. Petrified Fossils
 Fossils in which minerals
replace all or part of an
organism.
 How does this happen?
 Water rich in dissolved minerals
seeped into spaces, then
evaporated, leaving the hardened
minerals behind.
 Example – petrified wood

10. Molds and casts
 Most common type of fossil.
 Both copy the shape of the organism.
 A mold is a hollow area of sediment in the shape of
the organism.
 A cast is a copy of the shape of an organism.
Cast fossil
Mold fossil
Consider this:
Mold and cast
fossils can be
compared to
a cake pan.
The pan is the
mold, and the
cake is the
cast.

11. Carbonization-Carbon Films
 Leaves extremely thin coating of carbon film outline on
rock.
 How does this happen?
All organisms are made of carbon.
When they are buried,
the materials that make up
the organism evaporates.
These gases escape
leaving carbon behind.

12.  Trace fossils are a fossilized mark that is formed in soft
sediment by the movement or actions of an animal.
 Examples
 A footprint provides clues about the size and
behavior, the speed, how many legs it walked on,
lived alone or with others.
 A trail or burrow can give clues about the size and
shape of the organism, where it lived, and how it
obtained food.
Trace Fossils

13. Index Fossils
 An index fossil is a fossil found in a narrow
time range but widely distributed around the
earth; used to date rock layers.
 Example
 Trilobite: a marine organism that has become a fossil.
 Ammonite

16. Preserved remains
 Preservation of
remains with
little or no
change.
Bog
Mummies

17. Preserved remains
 Tar
 The sticky oil that
seeps from
Earth’s surface.
Tar soaks into the
organisms bones,
preserving the
bones from decay.

18. Preserved remains
 Amber
 The hardened
resin, or sap, of
trees. The
amber seals the
organism from
the air
protecting it
from decay.

19. Preserved remains
Ice
 Ice Fossils are actual flesh remains of
the organism. They become
trapped in ice and
remain frozen until
they thaw. A good example
of an ice fossil is a
Woolly Mammoth,
which are often
found in the Arctic.

20. NOW- Answer the following questions in
the margins below the notes.
Observe the fossil at the left.
A. What does it look like?
B. what type of fossil is it?
These fossils are believed to be found in the
Sahara Desert;
C. What might you infer about how they got
there?
Begin working on your Fossil stations.