1. Evidence for evolution
Geologic
Structural
Genetic

2. Geologic evidence: Geologic timeline from fossils Continental Drift
Plate tectonics

5. Continental Drift

6. Evidence for evolution:
Fossils
Observation: Fossils have been found and dated.
Inference: Comparing fossils to living species today indicates living organisms have changed over time.
Trilobite (extinct marine invertebrate) found in Ohio—site of an ancient sea

7. Fossils can form in several ways.
1. Permineralization
The minerals form a covering over the bones.
Permineralized skeleton of a Velociraptor dinosaur

8. Natural cast
Minerals fill in the spaces left from decomposition, recreating the original shape.
Cast of a crinoid, a marine animal

9. 3. Trace fossils. Leaf imprints Footprints
Fossils of footprints from a Dimetrodon dinosaur

10. Amber-preserved fossils organisms are trapped in tree resin
Wasp

11. an entire organism becomes encased in ice, volcanic ash, or mud.
Preserved remains
an entire organism becomes encased in ice, volcanic ash, or mud.
Ice preserved 5000 year old man found in the Italian Alps.

12. Specific conditions are needed for fossilization.
Only a tiny percentage of living things became fossils
Nevada’s state fossil: the icthyosaur which is the ancestor of the dolphin
We have the Icythyosaur State Park in central Nevada as Nevada was once underwater

13. Fossils: Links to the past…
Scientists have an incomplete picture of past life on Earth because:
Not all bones become fossils.
- Conditions
- Predated by animals
We have not found all fossils

14. Dating the age of Fossils
Law of superposition
Estimates the age of fossil
It compares the placement of fossils in layers of rock.
Radioactive isotope dating (Uranium used for really old aging Carbon 14 dating most common)

15. Law of Superposition

16. Radioactive dating