1. The Fossil Record

 When you think “fossil,” what comes to mind?  Oh,I know…  Fossil  Fossil – any part or trace of a once-living organism ◦ Many types…

Trace fossils include burrows, tracks, even fossilized poop! Fossil burrows Dinosaur tracksDinosaur & Fish Poop

Amber Amber is fossilized tree sap. It often traps pollen, insects and other small animals. Insects trapped in amber.

Petrified Wood When wood is buried in ash or sandy sediments, silica can form within the wood structure, eventually replacing the organic material. These petrified logs are found at Petrified Forest National Park in Arizona.

Molds/Castings Molds and castings form when the hard shell or exoskeleton of an organism is buried in sediment. The sediment hardens around the body, then the body dissolves or decomposes, leaving a void or mold. The mold can fill with minerals to form a cast in the shape of the mold. Casting of a fossil trilobite

Frozen Organisms In some places, animals and plants get trapped in snow and are preserved for thousands of years. This obviously happens only in cold mountainous and polar areas. Above - Otzi, the famous “Ice Man” found frozen in the Italian Alps Left - Dima, a baby mammoth found preserved in the Siberian permafrost by Russian miners.

Imprint Fossils When plants and animals fall in fine sediments, their bodies can sometimes leave an imprint that shows up when the resulting rock layers are split apart. Clockwise from left - The imprints of feathers can be seen in the Archaeopteryx fossil. A dragonfly imprint in the same fine sediment bed. The delicate imprint of an extinct fern’s frond.

Fossil Bones Bones and teeth of vertebrates are resistant enough to remain intact when the rest of the body has decayed. Dinosaur skeletons are among the most spectacular fossils ever found. A 12,000 year old mammoth skeleton Sue, the largest, most complete T. rex fossil ever found. It resides at the Field Museum in Chicago.

1. Burgess Shale 1. Burgess Shale – Canadian Rockies  Oldest: 500 mya (Cambrian Explosion); trilobites

2. Dinosaur National Monument 2. Dinosaur National Monument – CO/UT border  dinosaur bone deposit (150mya)

3. Fossil Butte 3. Fossil Butte - Wyoming  Ancient lake bed full of fossil fish  50 mya, Palm Tree Fossils (Tropical Area)

4. La Brea Tar Pits 4. La Brea Tar Pits – Los Angeles  Ice age mammals, 10,000-40,000 ya Ground Sloths Sabertooth Cats Columbian Mammoth

 Relative Dating  Relative Dating –compare fossil placement with fossils in other layers of rock ◦ No absolute age; only older/younger

 Radioactive Dating  Radioactive Dating – measuring the amount of remaining radioactive isotopes in a sample ◦ Absolute age ◦ Half-Life ◦ Half-Life – length of time required for HALF the radioactive atoms to decay  Ex. Carbon-14 begins to decay when an organism dies (HL = 5730 yrs). The remaining amt is compared to the amt of Carbon-12 to determine the age.

1. Plants and animals change 2. Environments change 3. Immense time span 4. Extinction is the fate of a species