Exploring Fossils: Molds, Casts, and Imprints

Upon viewing the Exploring Fossils video series, students will be able to do the following: Explain that fossils are the ancient remains or traces of once-living things. Understand that fossils come in a wide range of shapes, sizes, and forms. Define paleontology as the scientific study of fossils and ancient life. Understand that paleontologists are scientists who study fossils and ancient life. Describe how fossils help us understand the history of life on Earth. Explain why fossils are sometimes referred to as "windows to the past." Cite some of the following conditions necessary for fossil formation: quick burial by sediments; the presence of hard parts, such as teeth and bones; and the importance of remaining undisturbed for long periods of time. Explain that petrification is the process by which cells in once-living things are replaced by minerals. List examples of petrified objects, including wood, shells, and bones. Define imprints or impression fossils as those left by the mark of a living thing. Describe a mold as a hollow area in the shape of an organism left in sediment. Explain that a cast is a copy of the original shape of an organism that is formed when a mold is filled in with sediment and then hardens. List some of the ways ancient life forms have been preserved. Examples include preservation in tar pits, freezing, and preservation in amber. Cite a couple of ways we use fossils. Examples include the burning of oil, natural gas and coal; and utilizing cement for construction purposes.