1. { Looking at Fossils Chapter 2.1

2.  If the half-life of Uranium-232 is 70 years, how many half lives will it take for 10g to be reduced to 1.25g?  Mercury-197 is used for kidney scans and has a half life of 3 days. If the 32g of Mercury-197 is ordered, but takes 15 days to arrive, how much would arrive in the shipment?  Is radioactivity an example of relative or absolute dating? Why? Warm-up

3.  The remains or traces of physical evidence of an organisms preserved by key geologic processes is called a fossil.  Fossils are important because they give us clues about the past  Most fossils are hardened animal remains such as shells, bones, teeth, and skeletal body parts  Other fossils are impressions or preserved organisms found in rock Looking at Fossils

4. 1. Conditions have to be just right for fossils to from in rock 2. Organisms must be preserved before it decomposes or disappears  Usually soft parts decays too fast, which is why fossils only really show hard parts of plants and animals 3. Fossils form in the layers of sedimentary rock So How Are Fossils Formed

5.  Fossils that are the actual bodies or body parts of organisms are called original remains  Original remains are found in places where conditions prevent the decomposition or breakdown to occur Original Remains

6. 1. Ice – best preserver of prehistoric life. Ice has preserved original remains of things such as a 10,000 year old mammoth which have been found with bones, muscles, skin, and hair still in place 2. Amber – formed from the sticky substance inside trees that flows like syrup. If an insect is caught in the sap, the sap will cover the insects entire body and harden. 3. Tar – thick, oily pool of liquid. Things such as saber toothed cats and other animals were trapped and preserved Types of Original Remains

8.  If an organism is caused by or buried in sediment it may become a rock  Some fossils are not original remains or actual body parts, instead they are impressions or traces made in rock. Fossils in Rocks

9. Molds and Casts:  A mold is a visible shape that was left after an animal or plant was buried in sediment and then decayed away.  A cast is an object that is created when sediment fills a mold and becomes rock. Types of Rocks

10. Mold or cast?

11. Petrification  The process in which minerals pass through and replace the organisms cells with minerals which produces a stone-likeness to the object. Commonly happens with trees that die and are covered in sediment Carbon Films  Carbon is found in every living thing. Sometimes when a dead plant or animal decays, a visible carbon layer is left behind. These show the soft parts of these organisms that are rarely seen in other fossils Types of Rocks

12. Trace Fossils  Preserved evidence of animal activity or movement Examples:  Tracks – which tells us the size of animal and speed  Burrows – shelters made by animals buried in sediment  Feces – preserved animal poop Types of Rocks

13.  Index fossils lived in many areas but only existed during specific time spans  These characteristics make it extremely helpful when trying to date the age of a specific rock layer. Special Type of Fossils

14. Activity # 1  Obtain Set A materials: 8 index cards or slips of paper with letters on them.  Each slip of paper represents a rock layer.  Each letter represents a kind of fossil.  Your task is to determine what the correct sequence of the letters are, from oldest to youngest.

15. Questions: 1.What letter is the oldest? 2.What letter is the youngest? 3.What letter showed up the most? 4.Which letters only showed up once? 5.Which letters could be index fossils? 6.How did you know which was older: “M” or “X”?

16. Ice core video  http://teachertube.com/v iewVideo.php?video_id= 240111 http://teachertube.com/v iewVideo.php?video_id= 240111 http://teachertube.com/v iewVideo.php?video_id= 240111

17. So what do they tell? One big thing they tell us is the connection between CO 2 and climate long time ago. One big thing they tell us is the connection between CO 2 and climate long time ago. When looking at ice core samples, scientist use bubbles of past atmosphere as indicators of past life. When looking at ice core samples, scientist use bubbles of past atmosphere as indicators of past life. This helps us analyze and determine past levels of greenhouse gases, which helps us understand temperature This helps us analyze and determine past levels of greenhouse gases, which helps us understand temperature