Fossils: Our Keys to the Past and Evidence of Evolution

1. Fossils: Our Keys to the Past and Evidence of Evolution Chapter 7.2

2. Evidence of Evolution Similar body structures Patterns of early development Molecular structure Fossils!!

3. What is a fossil? “Paleo-” = old or ancient ; “-ology” = study of • Fossil: remains of ancient life • Comes 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

4. Why are fossils important? • Let scientists see extinction in different species • Gave Darwin evidence that earth is older than previously believed • very slow changes over a long period of time can add up to substantial changes in organisms

5. Giant Sloth vs. Living Sloth

6. Size Comparison (“same” bone next to a quarter)

7. Why are fossils important? • Give relative ages of rocks • correlate and match up rock units from different places • Evidence of continental drift – the theory that continents were once one large landmass

8. *Distribution of plant and animal fossils give evidence of supercontinents Plummer et al 2003

9. *Pangaea breakup and continental drift Plummer et al 2003

10. Fossilization “-ization” = to make BURIED IN SEDIMENT OR SOIL • 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

11. 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

12. Types of Fossils • Impressions– casts and molds • organisms leave an imprint in sediment • Traces – other evidence that an organism existed • ex. tracks, trails, footprints

13. 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

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

15. Radioactive Dating and Geologic Time Scale

16. Age on Earth • 4.6 to 4.7 billion years old • From *evidence* • Evidence is gathered from radioactive dating of rocks from the earth, moon and meteorites

17. Age on Earth • Relative age: places rock units or geologic events in sequential order • Ex: “My phone is older than his.” • Absolute age : numerical or chronological age of a rock or geologic event • Ex: “My phone is 2 years old and his is a week old.”

18. Newest layer Oldest layer

19. Radioactive Dating Definitions • Radioactive dating – a way of determining the age of rocks and fossils on a scale of absolute time • based on the half-life of radioactive isotopes • Radioactive isotope - an atomic form of a chemical element that is unstable

20. Radioactive Dating Definitions Radioactive decay - the spontaneous nuclear disintegration of certain isotopes Half-life – the time it takes for ½ the atoms of the radioactive parent to decay to atoms of the daughter element