1. Evolution: The Science behind the theory Geological time Fossils
Darwin & Natural Selection
Species changing over time
Anatomical & Embryological evidence
Speciation

2. Summary of Evolution of Life
Formation
of the
earth’s
early
crust and
atmosphere
Small
organic
molecules
form in
the seas
Large
(biopolymers)
First
protocells
Single-cell
prokaryotes
eukaryotes
Variety of
multicellular
organisms
form, first
in the seas
and later
on land
Chemical Evolution
(1 billion years)
Biological Evolution
(3.7 billion years)

3. How do we know
about the past?
Fossils

4. 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.

5. 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

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

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

8. 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.

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

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

11. 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

12. Where are fossils found?
Sedimentary
Rock
What type of rock formation is this? Sedimentary, Metamorphic, or Igneous? Sedimentary, you can see the layers. 12

13. 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. 13

14. What conditions promote fossilization?
Hard body parts such as skeletal bones or exoskeletons
Rapid burial and/or lack of Oxygen

15. Unaltered - insects or plant parts trapped in amber or ice ; original unaltered material from the living organism
Replacement – the hard parts of an organism dissolve and are replaced by other minerals
Petrification – rock-like minerals seep in slowly and replace the original organic tissues
unaltered preservation (like insects or plant parts trapped in amber, a hardened form of tree sap) original, unaltered material from the living organism
replacement (An organism's hard parts dissolve and are replaced by other minerals, like calcite, silica, pyrite, or iron)
petrification (in which rock-like minerals seep in slowly and replace the original organic tissues with silica, calcite or pyrite, forming a rock-like fossil - can preserve hard and soft parts - most bone and wood fossils are permineralized)
authigenic preservation (molds and casts of organisms that have been destroyed or dissolved).
Authigenic- molds or casts of organisms tissue material is decomposed or of markings left behind by an orgasnism

16. Putting it all together
Examples of Fossils . . . 16

17. Sporadoceras Nautilus
Sporadoceras, which lived during the Devonian period 350,000,000 years ago, are extinct relatives of the chambered nautilus.  The shells of these creatures accumulated on the sea floor and were buried in sediment.  Over the ages they hardened to stone.  Today they are quarried from what is now the Sahara Desert in Morocco.
Nautilus 17

18. Orthoceras
Orthoceras were marine, or sea animals similar to modern squid.  They had a shell shaped like a cone.  Orthoceras were active swimmers in warm shallow seas and swam by squirting water out of the body cavity.  They ate small animals and some grew to be 6 feet long.  In the fossilized remains of the shell, you can often see different chambers where the animal lived
Squid 18

19. Trilobites
Scientists think that trilobites were the first multiple-celled animal to exist on earth.  These extinct sea animals had exoskeletons, or outer armor, that was divided into 3 parts.  Some crawled on the sea bed, some floated and some swam.  The lived all over the world.  Crabs and lobsters are modern relatives.
Lobster 19

20. 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 20

21. 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. 21