1. How do we know
about the past?
Fossils

2. What is a fossil? A fossil is an impression, cast,
original material or track of any animal or plant that is preserved in rock after the original organic material is transformed or removed.

3. Material that has replaced the once living thing
A fossil may be:
an original skeleton or shell;
a mold or cast;
traces such as footprints or worm tubes
Material that has replaced the once living thing

4. Types of Fossils Body fossils – actual parts of an organism
bones, shells, leaf imprints

5. Types of Fossils Trace fossils –
evidence of life having been there tracks, burrows, casts

6. Trace Fossils
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
Molds and casts are actually two common types of trace fossils. A mold forms when something is pressed into soft mud and removed by decomposition or pulled out, leaving an impression of the object. A cast is a 3-D example of an object of the past created when a mold fills up with sediment like mud, sand or volcanic ash.

7. Trace Fossils Burrows or borings –
Spaces dug out by living things & preserved as is or filled in
Tracks –
impressions of passage of living things

8. Trace Fossils Imprint –
Thin objects such as a leaf that falls onto sediment & leaves an imprint then the sediment hardens into rock

9. Petrified Fossils Amber & Ice Minerals penetrate & replace the hard
parts of an organism producing a copy of them
Amber & Ice
An entire organism was quickly trapped in ice or tree sap that hardens into amber

10. Where are fossils found?
Sedimentary
Rock
What type of rock formation is this? Sedimentary, Metamorphic, or Igneous? Sedimentary, you can see the layers. 10

11. Why sedimentary rock?
The animal dies and lies on the ground or sinks to the sea floor.
The body begins to decay and is buried under layers of sediment such as mud or sand.
These layers eventually become sedimentary rock. 11

12. Putting it all together
Examples of Fossils . . . 12

13. Fossil Fish
Fish are the oldest and most primitive type of vertebrate.  The first fish were small, the size of a minnow.  They had heavy, bony plates for skin.  They lived on the ocean floor and are through slits on both sides of their throats.  Later, fish began to develop gills, scales and fins and learned to live in fresh water, too.  Some even developed lungs.  Over half the species of vertebrates, both living and extinct, are fish 13

14. Dinosaur Bones
The word dinosaur means "terrible lizard".  Dinosaurs  were reptiles that lived throughout the world and dominated the land for over 140 million years.  Some were as small as a rooster in size.  Other grew to be the largest land animals ever to live and weighed up to 80 tons.  Many dinosaurs ate plants.  Others were meat eaters.  They began to die out when the Earth's climate became colder and plant life changed. 14