Fossils: Our Keys to the Past and Evidence of Evolution

1. Fossils: Our Keys to the Past and Evidence of Evolution By: Shannon Reardon Adam Bouchardand Kristan Brodie http://www.kpbsd.k12.ak.us/chapman/demers/images/collage2.JPG

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 groundincluding minerals and archeological artifacts • In the 18th centurypaleontology (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 thatearth 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 showsevidence 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. Unaltered Parts Altered remains Carbonization of a leaf http://www.studyworksonline.com/cda/image/preview/0,1127,1309,00.jpg http://www.fp.sfasu.edu/geology/GeologyTutorial/Fossils/CARBONization01.JPG Impression - Cast and Mold http://gpc.edu/~pgore/myphotos/fossils/cast&mold.jpg

10. Permineralization – petrified wood Trace fossil http://www.clas.ufl.edu/users/pciesiel/gly3603c/wood1.jpg http://www.dinosaursrock.com/SteveDiloposaurusFootPrint.jpg

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

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