Fossil direct or indirect evidence of ancient life

Fossil = direct or indirect evidence of ancient life preserved in rocks gastroliths http: //www. fossilmall. com/Fossil_Archive/Trace_Softbody_Fossils/Climactichnites/dfd 100 d-large. gif http: //www. gc. maricopa. edu/earthsci/imagearchive/coprolite. jpg

How does a dead organism become a fossil? Most organisms that lived in the past left no record of their existence. To become preserved as a fossil, an organism usually: • Has hard parts. • Is buried by sediment. • Escapes physical, chemical, and biological destruction after burial. BAD = burrowing (bioturbation), dissolution, metamorphism, or erosion …. A bias towards benthic (bottom dwelling marine life with hard parts)!

How does a dead organism become a fossil? Modes of Preservation: 1. original preservation (unaltered remains) http: //paleo. cortland. edu/tutorial/Taphonomy&Pres/Taph%26 Pres%20 Images/horseshoe. GIF http: //upload. wikimedia. org/wikipedia/commons/thumb/a/a 4/Misc_pollen. jpg/290 px-Misc_pollen. jpg http: //www. ambermine. com/images/page 1/18 m. jpg

Modes of Preservation: 2. altered remains (structurally or chemically altered) Direct Fossil Evidence Permineralization Direct Fossil Evidence Replacement http: //paleo. cortland. edu/tutorial/Taphonomy&Pres/preservation. htm http: //www. gc. maricopa. edu/earthsci/imagearchive/cephalopod. jpg

Modes of Preservation: 2. altered remains (structurally or chemically altered) Direct Fossil Evidence Carbonization http: //paleo. cortland. edu/tutorial/Taphonomy&Pres/preservation. htm

Modes of Preservation: 2. altered remains (structurally or chemically altered) Direct Fossil Evidence molds (external mold shown here) Direct Fossil Evidence molds (internal mold shown here – outer shell gone but internal septa visible) http: //www. getyourwebsitehere. com/fossils/images/fos_0011 a. jpg http: //www. clas. ufl. edu/users/pciesiel/gly 3603 c/external. jpg Direct Fossil Evidence cast and molds

What do we use the fossil record for? 1. Understand the evolutionary history of life http: //www. ruf. rice. edu/~leeman/Geo. Time. Spiral. gif

What do we use the fossil record for? 2. Determining relative ages of the rocks that contain them (biostratigraphy) and correlating rock units of the same age. Index fossils - especially good fossils for this purpose • wide geographic range (swam or floated) • evolved rapidly • easily identified

http: //pubs. usgs. gov/gip/geotime/fossils. gif

What do we use the fossil record for? 3. Interpreting past environments http: //www. geology. ohio-state. edu/~vonfrese/gs 100/lect 29/xfig 29_02. jpg http: //oceanworld. tamu. edu/students/coral/images/coral_reef_1. jpg http: //www. wsgs. uwyo. edu/Coal/coal_brochure/images/fig 1_swamp. jpg

How are fossils classified? Based on morphology (shape) and inferred phylogenic (family tree) relationships http: //www. anselm. edu/homepage/jpitocch/genbios/25 -07 -Hierarchical. Class-L. jpg