Fossils are the preserved remains of plants and animals that lived millions of years ago.

 life forms in ancient times.

1. Fossils are formed when a plant or animal dies and decays. 2. It is buried by sediment. 3. Over a long period of time, the sediment hardens into ROCK and preserves the shape of the organism. Fossils are usually found in sedimentary rock.

 A mold is a hollow area in sediment that is in the shape of an organism.  A cast is the opposite of the mold. It is in the exact shape of the organism.

 Formation of a mold and cast: molds and casts animationmolds and casts animation

 Dinosaur tracks Dakota Group, Dinosaur Ridge near Denver, Colorado  Footprints or other trace fossils show evidence of the organisms’ activities. The mud or sand that the animal stepped in has been buried by sediment and the sediment slowly became solid rock. We can tell an organisms size and shape as well as whether it travelled alone or in a group.

 3) carbon film  Carbonization (or distillation ) preserves plants or animals as a thin carbon film, usually in fine- grained sediments (shales).As organisms decay, gas is given off, leaving behind a “photo copy of the organism.” Fine details of the organisms may be preserved.

 Some fossil remains are preserved intact in tar or amber.  Fossils can also be preserved by freezing.

 fossils in which minerals replace all or part of an organism Petrified Logs from Petrified Forest. Photographed at the Smithsonian Institution Ntional Museum of Natural History, Washington, D.C.

 fossils tell climate condition fossils tell climate condition

 fossilization fossilization

 The gradual change of an organism over long period of time.

 An organism becomes extinct when none of its species is left on Earth.  2 main reasons for extinction :  A) habitat destruction  B) climate change  of_extinct_animals#Modern_extincti ons