Evidence for evolution Geologic Structural Genetic

Geologic evidence: Geologic timeline from fossils Continental Drift Plate tectonics

Continental Drift

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

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

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

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

Amber-preserved fossils organisms are trapped in tree resin Wasp

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.

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

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

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)

Law of Superposition

Radioactive dating