Fossil = direct or indirect evidence of ancient life preserved in rocks

http://www.gc.maricopa.edu/earthsci/imagearchive/coprolite.jpg

gastroliths

http://www.fossilmall.com/Fossil_Archive/Trace_Softbody_Fossils/Climactichnites/dfd100d-large.gif

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?

How does a dead organism become a fossil?

Modes of Preservation:

1. original preservation (unaltered remains)

http://www.ambermine.com/images/page1/18m.jpg

http://upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Misc_pollen.jpg/290px-Misc_pollen.jpg

http://paleo.cortland.edu/tutorial/Taphonomy&Pres/Taph%26Pres%20Images/horseshoe.GIF

Modes of Preservation:

2. altered remains (structurally or chemically altered)

Direct Fossil EvidencePermineralization

Direct Fossil EvidenceReplacement

http://www.gc.maricopa.edu/earthsci/imagearchive/cephalopod.jpg

http://paleo.cortland.edu/tutorial/Taphonomy&Pres/preservation.htm

Modes of Preservation:

2. altered remains (structurally or chemically altered)

Direct Fossil EvidenceCarbonization

http://paleo.cortland.edu/tutorial/Taphonomy&Pres/preservation.htm

Modes of Preservation:

2. altered remains (structurally or chemically altered)

Direct Fossil Evidencemolds

(external mold shown here)

http://www.clas.ufl.edu/users/pciesiel/gly3603c/external.jpg

Direct Fossil Evidencemolds

(internal mold shown here – outershell gone but internal septa visible)

Direct Fossil Evidencecast and molds

http://www.getyourwebsitehere.com/fossils/images/fos_0011a.jpg

What do we use the fossil record for?

1. Understand the evolutionary history of life

http://www.ruf.rice.edu/~leeman/GeoTimeSpiral.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.wsgs.uwyo.edu/Coal/coal_brochure/images/fig1_swamp.jpg

http://oceanworld.tamu.edu/students/coral/images/coral_reef_1.jpg

http://www.geology.ohio-state.edu/~vonfrese/gs100/lect29/xfig29_02.jpg

How are fossils classified?

http://www.anselm.edu/homepage/jpitocch/genbios/25-07-HierarchicalClass-L.jpg

Based on morphology (shape) and inferred phylogenic (family tree) relationships