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Notes on Earth/Space. S.W.B.A.T. List the conditions necessary for fossils to form List the conditions necessary for fossils to form Describe several.

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Presentation on theme: "Notes on Earth/Space. S.W.B.A.T. List the conditions necessary for fossils to form List the conditions necessary for fossils to form Describe several."— Presentation transcript:

1 Notes on Earth/Space

2 S.W.B.A.T. List the conditions necessary for fossils to form List the conditions necessary for fossils to form Describe several processes of fossil formation Describe several processes of fossil formation Explain how fossil correlation is used to determine rock ages Explain how fossil correlation is used to determine rock ages

3 Fossils Fossils are evidence of past life on Earth Fossils are evidence of past life on Earth Fossils are remains, imprints or traces of prehistoric organisms Fossils are remains, imprints or traces of prehistoric organisms Extinct animals are studied using their fossilized remains Extinct animals are studied using their fossilized remains

4 Ammonite Fossils – Extinct Since the Dinosaurs

5 Fossils Fossils can also tell how a species lived; reproduced and died Fossils can also tell how a species lived; reproduced and died Most organisms decay very quickly after death Most organisms decay very quickly after death Microorganisms such as bacteria cause remains to rot Microorganisms such as bacteria cause remains to rot

6 Fossils Soft parts (tissue, feathers and hair) do not fossilize easily Soft parts (tissue, feathers and hair) do not fossilize easily Hard parts (teeth, shell & bone) tend to preserve well over time Hard parts (teeth, shell & bone) tend to preserve well over time

7 Fossils Animals or organisms covered by sediment quickly after death also preserve well Animals or organisms covered by sediment quickly after death also preserve well Scavengers (usually) do not eat hard parts & cannot scavenge what is buried Scavengers (usually) do not eat hard parts & cannot scavenge what is buried

8 Types of Preservation Permineralized – remains that have been buried & replaced by minerals in groundwater Permineralized – remains that have been buried & replaced by minerals in groundwater

9 Types of Preservation Carbon film - organisms are buried by sediment then slightly heated & squeezed Carbon film - organisms are buried by sediment then slightly heated & squeezed A thin film of carbon residue is left “silhouetting” (or shadowing) the original organism A thin film of carbon residue is left “silhouetting” (or shadowing) the original organism

10 Types of Preservation Organisms with shells or other hard parts may form impressions in soft mud or sand Organisms with shells or other hard parts may form impressions in soft mud or sand Molds – buried hard part dissolves in the sediment leaving a cavity Molds – buried hard part dissolves in the sediment leaving a cavity

11 Types of Preservation Later, mineral-rich water or other sediment may enter the cavity (or mold) Later, mineral-rich water or other sediment may enter the cavity (or mold) Cast – when the sediment-filled mold is hardened into rock making a copy of the original organism Cast – when the sediment-filled mold is hardened into rock making a copy of the original organism

12 Types of Preservation Original remains – tar, amber & ice can preserve original tissue of an organism Original remains – tar, amber & ice can preserve original tissue of an organism Sometimes original remains & the DNA of the animal is also preserved (ex. Dinosaur bones) Sometimes original remains & the DNA of the animal is also preserved (ex. Dinosaur bones)

13 T-Rex Femur Bone Found to Have Original DNA

14 Types of Preservation Trace – fossil trails, burrows & footprints that have hardened in rock Trace – fossil trails, burrows & footprints that have hardened in rock Rock was once silt/mud or a volcanic ash layer before solidifying Rock was once silt/mud or a volcanic ash layer before solidifying

15 Which Dinosaur Made These Tracks? Video (1:42) “Dinosaur Tracks Uncovered in ArkansasVideo (1:42) “Dinosaur Tracks Uncovered in Arkansas” Video (1:42) “Dinosaur Tracks Uncovered in Arkansas

16 Types of Preservation Index fossils – tells exactly where & when a species existed (ex. Graptolites) Index fossils – tells exactly where & when a species existed (ex. Graptolites) Index fossils can be used to determine the ages of the rock layers they are found in Index fossils can be used to determine the ages of the rock layers they are found in Fossils also tell us about ancient environments & shallow seas (ex. Crinoids) Fossils also tell us about ancient environments & shallow seas (ex. Crinoids)

17 Relative Dating and Index Fossils What is relative dating? What is relative dating? ◦ Any method of determining whether an event or object is older or younger than other events or objects. What is an index fossil? What is an index fossil? ◦ A fossil that is found in the rock layers of only one geologic age and is used to establish the age of the rock layers. ◦ Is found in rock layers around the world, ex Trilobites

18 Class Activity Explain how some wooly mammoths have been found preserved intact in frozen ground Explain how some wooly mammoths have been found preserved intact in frozen ground What type of fossil preservation occurred and what conditions must have persisted since these animals went extinct? What type of fossil preservation occurred and what conditions must have persisted since these animals went extinct?


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