Chapter 12 Clue's to Earth's Past Section 12-1 Fossils

The Fossil Record Fossils are a key to the past, they provide information about past environments (paleoecology), the geology of the area, climate, and living conditions.

http://www.ucmp.berkeley.edu/fosrec/fosrec.html

http://www.stonejungle.com/fossil-birds.htm

Fossil formation occurs if:

1. Remains are buried soon after death

2. The organism has hard parts (bones, shells, etc.)

Value of fossils -

1. Determine relative geologic age

2. Shows course of natural selection

3. Shows changing environments and patterns

 
Fossil types:
Original remains - the entire organism is intact (mummies, mammoth) conditions necessary for their formation are lack of bacteria and some type of entrapment.

Replaced remains -

substitution of one chemical for the organic material that made up the organism when it was alive. Petrified wood (silica) Calcite shells (pyrite)

Carbonization -

tissue of plants and animals is transformed to a thin film of carbon. The organism has to be thin (leaves, fish)

Molds, casts, and imprints -

the mold is the cavity, the cast is the deposited mineral that fills the cavity, the imprint is similar to a mold but shallow.

Trace fossils -

tracks, trails and burrows. (dinosaur tracks)