Fossils as Preserved Remains

Types

• Body fossils, which once had organic matter, include bones, shells and teeth. Trace fossils, created from the imprint of a plant or animal, include footprints, dung or trails.

Preservation

• Fossils usually occur when material is buried under layers of mud or sand that gradually transform into sedimentary rock. Fossils can also be created from being frozen, dried out or trapped in amber or tar, or they can be preserved in volcanic ash.

Size

• Fossils range in size from tiny plant spores to enormous dinosaur bones, which can measure 10 feet long.

Significance

• Fossils help scientists trace the path of evolution by examining how organisms have changed over time. However, since only a very small percentage of organisms become fossilized, the fossil record is not always conclusive or complete.

Time Frame

• Scientists have found evidence of microscopic organisms in Greenland that existed 3.7 to 3.8 billion years ago.