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Teachers' Domain - Digital Media for the Classroom and Professional Development Search Teachers' Domain Go User: My Folders Loading... Create a new folder Upload Media My Groups No groups created yet. Create a new Group Join a Group My Profile HELP | SIGN OUT Please sign in for full access This Teachers' Domain feature requires registration, which is simple, safe, and free. Register Now Citation "Becoming a Fossil." Teachers' Domain. 26 Sep. 2003. Web. 3 Feb. 2012. .

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Signing in now will connect your and Teachers' Domain accounts, so that in the future you will automatically be signed into Teachers' Domain when you come from . Becoming a Fossil Resource for Grades 6-12 | Citation Media Type: Video Running Time: 2m 34s Size: 3.5 MB View SAVE TO FOLDER Loading... Save Cancel Share | Source: NOVA: "In Search of Human Origins" Resource Produced by: Collection Developed by: Collection Credits Collection Funded by: See Also: National K -12 Subject: Deep Time/History of Life Evidence for Evolution Lesson Plans Using this Resource: Evidence for Evolution The Fossil Evidence for Evolution Fun with Fossils The remains of the vast majority of organisms that die are eaten by scavengers or decompose beyond recognition before they can be preserved. The conditions under which fossils can successfully form are unusual, and the odds that a fossil will then be exposed at the surface again, and discovered, are smaller still. Footage courtesy of NOVA: "In Search of Human Origins." Alternate Media Available: Becoming a Fossil (Audio Description) (Video) Accessibility Features: Audio Description, Caption, Transcript Background Essay The study of how life evolved would be impossible if not for the history that is told in the fossilized remains going back billions of years. Scientists have described about 250,000 different fossil species, yet that is a small fraction of those that lived in the past. The oldest fossils are remains of marine organisms that populated the planet's oceans. When they died, the plants and animals were buried by mud, sand, or silt on the sea floor. Land animals and plants usually decomposed or were eaten, and mainly the hard parts -- teeth, bones, shells, or wood -- were preserved. Fossils can be formed in several ways. Buried bone and shell contain tiny air spaces into which water can seep, depositing minerals. Reinforced by these mineral deposits, bone and shell can survive for millions of years. Even if the bone or shell dissolves, the mineral deposits in the shape of the body structure remain. Besides rock, fossils may be found as the result of an organism being entombed in ice, tar (like the famous La Brea Tar Pits in Los Angeles), or amber, in which ancient insects have been found, wonderfully preserved. Rare but highly informative are fossils created by a sudden event, like a volcanic eruption, that traps living things or, in the famous case in Laetoli, Ethiopia, footprints of human ancestors millions of years old. Fossil remains come to the attention of scientists when they are exposed at Earth's surface. Erosion, land movements, or excavations often have revealed important fossil finds. Especially rich fossil troves are called Lagerstatten, a German word meaning storehouse. These are localities where conditions were right to preserve even soft-bodied animals, and they allow scientists to read a key portion of life's history. In the famous Burgess Shale in Canada, for example, scientists have found dozens of bizarre, previously unknown animals. Interpretation of fossils poses another set of challenges, and their age can only be estimated by radiometric dating of rocks they were found near or within. Discovery of fossils is only the beginning of mining their secrets. Plot locations of important African finds in the search for early human remains in this NOVA classroom activity. Print Background Essay Discussion Questions Discuss the rather restricted set of circumstances under which a large mammal, such as an early hominid, could first become fossilized and then be discovered by researchers. How might conditions for successful fossilization differ between mammals and plants? Why? Discuss how different organisms living in different niches might have very different probabilities of being fossilized. Print Discussion Questions Transcript NARRATOR: It takes a rare set of circumstances to turn a living creature into fossilized bone. In the case of Lucy, the famous hominid fossil discovered in Ethiopia's Great Rift Valley in 1974, there is no evidence that she met a violent death. No predator or scavenger found her body before it began rotting in the lake's soft sediments. Her bones, which settled in the mud, may have been cracked or shattered by animals roaming around the shore. Heavy rains gradually washed in enough sand and gravel to bury her bones. These deposits built up over thousands of years, burying her remains hundreds of feet deep. The calcium in her bones, molecule by molecule, was replaced by minerals from these deposits, the bones to stone. She remained buried over millions of years, while the earth's crust moved constantly, forcing the remains of her body closer to the surface. Heavy storms beating down on the earth eroded the sediment and most likely brought her once again to the earth's surface. Her exposure made it possible for anthropologists to later discover her remains some three million years after her death. (thunder rumbling) Print Transcript Standards About Standards | Report a Standards Mismatch About Standards | Report a Standards Mismatch About Standards | Report a Standards Mismatch   close Report a standards correlation problem To help improve this service, please report and describe any standards correlations that you find to be inaccurate. close About standards correlation Academic standards correlations on Teachers' Domain use the Achievement Standards Network (ASN) database of state and national standards, provided to NSDL projects courtesy of JES & Co. 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