Fossils: Windows into the Past Essential Question: Explain the use of fossils as evidence of Earth’s history and its life forms.

Vocabulary Paleontology Fossil Fossil Record Mold Cast Petrified Preserved Carbonized Trace Trilobite

Concept Uses of Fossils Types of Fossils

Paleontology The study of fossil evidence to learn about ancient life forms.

Fossil The preserved remains of organisms that lived in the distant past. Can also be evidence of organisms’ behaviors that were preserved.

Fossil Record The evidence provided by fossils about what Earth was like millions of years ago. Clues provided include: Climate & atmosphere changes. Geology – plate tectonics, erosion. Diversity of life on Earth – different organisms that have lived and how they have changed.

#1 – Mold Fossil Sediments bury an organism and change into rock. Over time the organism decays and leaves a cavity (hole) in the shape of the organism.

#2 – Cast Fossil When a mold fossil is filled with sand or mud that hardens into the shape of the organism.

#3 – Petrified Fossil When minerals soak into buried remains, replace the remains, and then change into rock.

#4 – Preserved Fossil Forms when organisms do not decay at all because they are trapped in ice, tar, or amber.

#5 – Carbonized Fossil Body parts like leaves, stems, and flowers are pressed between layers of soft mud that hardens. It squeezes away the decayed organism leaving only an imprint.

#6 – Trace Fossil Mud or sand hardens into stone where a footprint, trail, or burrow of an organism was left behind.

Example: Trilobite Ranged in size from 1-3 inches to 2-3 feet. Existed for almost 300 million years. Went extinct about 250 million years ago. Related to today’s horseshoe crabs.