1. Fossils: Our Keys to the Past and Evidence of Evolution
By: Shannon Reardon Adam Bouchard and Kristan Brodie

2. What is a fossil? A fossil is remains of ancient life
Fossil is derived from the Latin term fossilis - meaning any object extracted from the ground including minerals and archeological artifacts
In the 18th century paleontology (the study of ancient life) was created
paleo
ology
= old or ancient = study of

3. Why are fossils important?
It enabled scientists to see occurrence of extinction in different species
It gave Darwin evidence that earth is older than previously believed and that very slow changes over a long period of time can add up to substantial changes in organisms
Can be used to correlate and match up rock units from different places giving relative ages
It shows evidence of continental drift – the theory that continents were once one large landmass

6. Plummer et al 2003

7. Fossilization ization
= TO MAKE
Hard parts of organisms are more likely to be preserved than soft parts.
Soft parts are likely to decay or be consumed by other organisms
Because of this soft bodied creatures such as jellyfish may not be fossilized either
Buried organisms are more likely to be fossilized because it minimizes the decay, consumption, and destruction of the remains
BURIED IN SEDIMENT OR SOIL

8. Types of Fossils
Unaltered remains – original material of the organism has not been changed to another substance
Altered remains – original material has undergone permineralization, recrystalization, replacement, carbonization
Impressions – organisms leave an imprint in sediment, can form casts and molds
Traces – other evidence that an organism existed, ex. tracks, trails, footprints

9. Altered remains Carbonization of a leaf
Unaltered Parts
Altered remains Carbonization of a leaf
Impression - Cast and Mold

10. Permineralization – petrified wood Trace fossil

11. Radioactive Dating and Geologic Time Scale
By Adam Bouchard

12. Age on Earth
EVIDENCE suggests age of the Earth is about 4.6 to 4.7 billion years old
Evidence is gathered from radioactive dating of rocks from the earth, moon and meteorites
Relative age : places rock units or geologic events in sequential order
Absolute age : numerical or chronological age of a rock or geologic event

13. Radioactive Dating Definitions
Radioactive isotope - an atomic form of a chemical element that is unstable
Radioactive decay - the spontaneous nuclear disintegration of certain isotopes
Radioactive dating – a way of determining the age of rocks and fossils on a scale of absolute time. It is based on the half-life of radioactive isotopes
Half-life – the time it takes for ½ the atoms of the radioactive parent to decay to atoms of the daughter element

14. Newest layer
Oldest layer