Inside the Restless EarthChapter 3 Section 4

A fossil of a preserved remains of once living organisms.

Fossils give clues about organisms that lived long ago. They help to show that evolution has occurred.

They also provide evidence about how Earth’s surface has changed over time.

Fossils help scientists understand what past environments may have been like.

A:Fossils are the remains of organisms that are preserved.◦Hard parts (bones, shells) get buried in sediment

◦Soft parts of the organism decays

A:Petrifaction is the process in which minerals replace an organisms tissues.◦Replacement-organism’s tissues are completely replaced by minerals

◦Permineralization-minerals fill spaces

A: An organism gets stuck in soft, sticky tree sap and then gets covered in more sap. The sap then hardens.◦Hardened tree sap is called amber.◦Insects, frogs, lizards have been found in

amber.◦Organism land on sap◦Gets stuck◦Gets covered in more sap◦Sap hardens

A: Frozen fossils are the remains of organisms that have been preserved in ice. Usually during the ice age.◦Cold temperatures slow down decay

◦Organism falls-freezes◦Makes good fossils

A: Fossils are in asphalt because organisms got stuck in the thick, sticky substance.◦La Brea asphalt/tar pits in California are over 38,000 years old.

◦Scientists learned a lot about the past environment in California.

La Brea Tar Pits

A: These form when animal footprints, burrow, or coprolite are filled in with sediment and are preserved in rock.◦Tell how big the animal was◦How fast the animal moved◦Borrows that animals made are an example

◦Coprolite is preserved animal dung

A: A mold is a cavity (hole-space) where a plant or animal was buried.

A: A cast is an object created when sediment fills a mold and becomes a rock.◦Mold-impression in ground or rock◦Cast—sediment filled mold

Internal and External mold

A: The fossil record provides evidence about the past.◦We know more about organisms with hard parts (ex. Shells)

◦The fossil record is incomplete.◦Many organisms never become fossils

◦Many fossil haven’t been discovered

A: Fossil records provide evidence of changes in the environment.◦Marine fossils were found on a mountain top. This suggests that the mountain top was once the ocean floor.

◦Fossils show evidence of climate

A: Fossils show how organisms have changed over time. Scientists study the relationship between fossils.◦Fossils in different rock layers suggest

that fossils can be younger or older depending on the layer they are found in.

◦Only a fraction of organisms in history have been fossilized = incomplete fossil record

• A: Fossils are used to date rocks because certain types of fossils can be used to estimate the absolute (exact) age of the sedimentary rock they are found in.• An index fossil is a fossil used to estimate

the absolute age of rock layers.• An index fossil lived for a short period of

time.• Ammonites and Trilobites (index fossils)

A:Mummification is the preservation of a body, either animal or human. ◦Some mummies are preserved wet, some are frozen, and some are dried.

◦It can be a natural process or it may be deliberately achieved.

◦Eliminate moisture