1. Evidence for Evolution
Fossil Introduction

2. Fossils
In biological terms, a fossil can be defined as evidence of an organism that lived some time in the past.
Are often found in sedimentary rocks

3. Fossilization Process
Few organisms become fossils
Organisms usually have to be buried in mud, sand, or clay soon after they die
Most fossils are found in sedimentary rock
These rocks form at relatively low temperatures and pressures that may prevent damage to the organism
Metamorphic rock and igneous rock undergo very physically demanding transformations that can incinerate and destroy organisms, which is why they do not typically contain fossils

4. The Fossil Record
Is the ordered sequence of fossils as they appear in rock layers
Reveals the appearance of organisms in a historical sequence
Fits with other evidence of evolution
Paleontologists study evolution

5. History of Paleontology
Paleontology began in the late 17th century when English naturalist, Robert Hooke examined fossils of marine creatures from England
Charles Darwin used the fossil record to form his explanation of the theory of evolution in the 1830’s

6. Transitional Forms Refer to diagram
Fossils show a succession from very simple forms early in the fossil record to much more complex forms that appear much later in the fossil record
Fossils show multiple examples of transitional forms

7. Fossils and Geological Time
Scientists will date the rocks in an attempt to determine the age of the fossil
Two ways to do this:
Relative dating: When you compare the depth of the layer of rock the fossil was formed in relative to other layers of rock
Radiometric dating: Uses isotopes

8. Relative Dating aka Law of Superposition
Relative dating uses layers to determine age by order of appearance
Relative dating will not give you a specific age in years, just relative to the layers above and below the fossil
Compare rock layers to layers of clothing in your laundry hamper…Oldest on the bottom (unless disturbed)

9. Radiometric Dating
Technique involves using radioactive isotopes, which are atoms with unstable nuclei that break down (decay) over time, giving off radiation
Most fossils cannot be directly radiometrically dated
Most dates are for volcanic or igneous rocks or metamorphic rocks that are closely associated with sedimentary rocks