Fossils

Key Vocabulary

FossilSedimentary Rock

Mold and CastPetrified Fossil

Carbon FilmTrace Fossil

Preserved FossilsPaleontologist

TheoryEvolution

Extinct

Fossils

Fossils are the preserved remains or traces of living things

Fossils like this fish provide evidence of how life has changed over time.

How Fossils Form

Sedimentary rock is the type of rock that is made of hardened sediment

Most fossils form when living things die and are buried by sediments. The sediments, like rock particles, remains of living things, limestone, sandstone and coal slowly harden into rock and preserve the shapes of the organisms

Sedimentary Rock DepositionSedimentary rock builds up through deposition when sediment are deposited on land, build up and harden into a layer of rock.

New layers of sediment build up and harden over the previous layers.

Sedimentary rocks seem to have stripes or layers of different types of rocks. This is called striation.

Sedimentary Rock Erosion

Layers get exposed when the rock through erosion when wind and water wear away the rock.

The layers with the fossils become the surface layer and the fossils become exposed. Fossils are discovered through erosion.

Paleontologists Are Scientists who Study Fossils

Paleontologists Collect fossils from sedimentary rock Determine what past life forms were like Classify organisms Arrange organisms in the order in which they lived

They do this to learn about the animals, the environments in which they lived, and to learn about the changes in the Earth’s surface.

Types of Fossils

Mold and Cast - Trilobite

Amber Fossils - Scorpion

Carbon Film – Plant

Tar Fossils - Millipedes

Trace Fossils- Dinosaur Footprint

Petrified Fossils – Shark Tooth

Ice Fossils - Mammoth

Mold and Cast

Mold and Cast fossils copy the shape of organisms.

A mold is a hollow area in sediment that is left what is left of a living organism dissolves after being buried in sediment.

A cast is a solid copy of the shape that is made from sediment that fills the mold.

Petrified Fossil

Petrified fossils are made when minerals fill in all of an organism’s organic matter, hardening the tissues and preserving the remains.

Carbon FilmsCarbon films are formed when the minerals within an organism dissolve or evaporate and all that is left are traces of carbon, an element found in all living things.

Trace Fossils

Trace fossils are preserved evidence of the activities of animals and plants.

These fossils burrows preserve ancient worms’

homes and tunnels

Early hominid footprints help scientists make theories

about body shapes and types

Corprolite – fossilized fecal matter – preserves information about diet

and eating habits

Preserved FossilsAnimals and plants that are frozen and covered by ice can be preserved whole, including hair and skin. They are preserved until the ice melts like this mammoth found in Russia.

Plants and animals, like this mosquito, can be caught in amber – hardened tree sap – and the tissue does not decay because it protected from air and weather.

Animals that became trapped in tar, or very sticky oil, were stuck and preserved from decay. This rhino was found in tar pits in Poland.

Using FossilsFossils occur in a particular order: the oldest rocks contain fossils of simpler organisms and the younger rocks contain fossils of more complex organisms. The fossil record shows that life on Earth has evolved, or changed over time.

A scientific theory is a well-tested concept that explains what scientists observe. Observations of the fossil record led scientists to the theory of Evolution. Evolution is the gradual change of living things over long periods of time.

One type of change that has happened gradually is that some animals no longer exist and will never again live on Earth. These animals are extinct.

Some Extinct Animals

This dinosaur from 66 million years ago was found in 2004 and named

Dracorex hogwartsia.

The Archelon was a 15 ft turtle that lived 65 million

years ago

The Doedicurus is an ancient armadillo that lived 11,000

years ago

Fossils are the only records we have of these species that are no longer living on Earth.