Chapter 9.1: Fossils

1. Chapter 9.1: Fossils Mr. Perez

2. Paleontologist • Fossil • Permineralized remains • Carbon film • Mold • Cast • Index fossil • Trace fossil Important vocabulary

3. A paleontologist is a scientist who studies fossils. • They can learn about extinct animals from their fossil remains • Paleontologists can use fossils to study the similarities and differences of organisms that lived in the past and compare them with those living today. Traces of the Distant Past

4. Sedimentary rock may contain fossils of plants, animals and even some microbes. • Fossils are the remains, imprints, or traces of prehistoric organisms • Fossils have helped scientists determine approximately when life first lived on land, and when organisms became extinct– they are evidence of not only when and where organisms lived, but also HOW they lived. Formation of Fossils

5. Conditions needed to form fossils: • Protection from scavengers and agents of physical destruction (waves, currents, wind) • Usually, a dead organism is protect by being buried under sediments • Dead organisms should have hard tissues such as bones, shells or teeth • Scavengers are less likely to eat these hard parts • These hard tissues also decay (break down) more slowly than softer tissue Formation of Fossils

6. Formation of Fossils

7. Mineral Replacement • Carbon Films • Coal • Molds and Casts • Original Remains • Trace Fossils Types of Preservation

8. Most hard tissues of an organism have empty spaces inside • Permineralized remains are fossils in which the spaces inside are filled with minerals from groundwater • Some original material from the fossil organism’s body might be preserved– sometimes, DNA can be extracted Mineral Replacement

9. Tissues of organisms are made of carbon • As an organism is buried, heat and pressure squeeze gases and liquids out • A carbon film forms when a thin residue is left, forming a silhouette of the original organism Carbon Films

10. Large amounts of plant matter accumulates in swampy areas… • After millions of years, these deposits become completely carbonized as COAL • We use coal for fuel • Coal is not a very good fossil to inform us of the plant’s past Coal

11. Impressions form when seashells or other hard parts of organisms fall into a soft sediment such as mud—which is buried by more sediment • Compaction and cementation turns this sediment into a sedimentary rock • Sometimes, there are holes in the rock that allow water and air to dissolve the hard part of the organism inside the rock, leaving a cavity called a mold • Later, mineral-rich water or other sediment might enter the cavity, form new rock and produce a copy or a cast of the original object Molds and Casts

12. Molds and Casts

13. Sometimes conditions allow original soft tissue of organisms to be preserved for thousands or millions of years. • Insects trapped in amber (hardened form of tree resin/sap) • Mammoths preserved in frozen ground in Siberia • Natural tar deposits, such as La Brea tar pits in California Original Remains

14. Trace fossils are fossilized tracks and other evidence of the activity of organisms • Tracks can tell you more about HOW and organism lived than any other type of fossil • Trails and burrows can also tell scientists about how animals lived Trace Fossils

15. Species have changed over time • Fossils help provide evidence of similarities and differences of organisms that lived in the past with those living today. • Some species have remained the same for very long periods of time, whereas some other species have changed a lot • These changing species are used as index fossils, or remains of species that existed • on Earth for relatively short periods of time • were abundant • were widespread geographically Index Fossils

16. We can use index fossils to estimate the age of rock layers Index Fossils

17. Fossils help scientists determine whether an area was land or whether it was covered by an ocean at a particular time • Fossils can also help determine the climate of a past region Fossils and Ancient Environments

18. Today, we will be starting a 2 day lab. This lab will help demonstrate how fossils are formed. • Each group should have the following MATERIALS: • Paper towels • Three slices of bread (one slice each of white, wheat, and grain) • 6 Gummy candy fish (or other gummy sea animals or plants) • Heavy books • Clear drinking straws (Day 2 only) Fossil Formation Lab

19. PROCEDURE (Day 1) • Remove and throw away the crust of each slice of bread • Place the slice of white bread on top of one paper towel. Place THREE gummy bears on top of the slice of bread. This represents the sandy sea floor with a dead organism. • Place the slice of grain bread on top of your white bread layer. This represents sediments deposited on top of dead material and settling on the bottom of the ocean. • Place the remaining gummy bears on top of the grain bread layer and the wheat bread on top of the gummy bears. This represents more dead material and sediments that are deposited on top of the bottom layers. • Fold over your paper towel, covering your stack of bread and gummy bears. • Place a textbook on top of your bread stack to represent pressure applied to the dead matter. Leave it under the text book for 2 days. Fossil Formation Lab

20. Fossil Formation Lab

21. PROCEDURE (Day 2) • Observe the bread fossil. Push a clear straw straight down into the bread and pull it back up to “extract” a core sample. Observe the layers through the straw. • Try to separate the layers of the bread. • Try to extract the bears. • Compare the colored residue of the gummy bear in the bread fossil to the remains of the plants and animals that seep into rock. The residue left by the gummy bear represents oil deposits left behind by dead ocean plants and animals. Over millions of years, these remains are pressurized to become oil and natural gas deposits. Fossil Formation Lab

22. Florida Science Grade 7 Glencoe Science & McGraw Hill Publishing • Google Images • http://www.earthsciweek.org/forteachers/2009/FossilFormation_Sept_cont.html Resources