Name______________________________
Section 3.4 Looking at Fossils
I.
Fossilized Organisms
a. The remains of physical __________________________________________________________
______________________________________________________________________________
i.
Most often preserved in _____________________________
b. Fossils in Rocks
i.
Dead organisms are quickly buried ___________________________________________
ii.
_____________ & _____________ from the organism are more resistant to decay
iii.
When sediments become rock, the ________________________ are preserved
c. Fossils in Amber
i.
Amber is hardened _______________________
ii.
_______________, _____________, & __________________ have been found in amber
d. Petrifaction
i.
Process in which__________________________________________________________
a. Permineralization – the pore space in ______________________________________
_____________________________________________________________________
b. Replacement – organisms tissues are completely replaced by ___________________
e. Fossils in Asphalt
i.
Pools of sticky liquid that trap organisms
ii.
La Brea asphalt deposits in Los Angeles, CA
f. Frozen Fossils
i.
Cold temperature slow decay, many frozen fossils from ___________________________
ii.
20,000 year old woolly mammoth found in _________________________
II. Other Types of Fossils
a. Trace Fossils
i.
Any naturally preserved ____________________________________________________
ii.
Examples
a. Tracks
b. Burrows – shelters made by animals, such as ______________
c. Coprolite – preserved ________________________________
b. Molds and Casts
i. Mold – a cavity __________________________________________________________
ii. Cast – an object created when sediment fills a mold and __________________________
III. Using Fossils to Interpret the Past
a. The Information in the Fossil Record
i. A rough sketch of _____________________________________________
ii. More information about organisms in environments that __________________________
iii. Incomplete record because _________________________________________________
b. History of Environmental Changes
i. Presence of marine fossils on a mountain top means______________________________
________________________________________________________________________
ii. Marine fossils help scientists reconstruct ancient ______________ & changing sea levels
iii. Plant and land animal fossils help to reconstruct past ________________ in an area
c. History of Changing Organisms
i. Studying relationships between fossils tell how life ______________________________
ii. Missing fossils provides an incomplete fossil record
iii. Paleontologists look for similarities between fossilized organisms and their
closest ______________________________
IV. Using Fossils to Date Rocks
a. Index Fossils – organisms that lived ________________________________________________
_____________________________________________________________________________
i. by dating _______________ above & below these fossils, a time span can be determined
b. Ammonites
i. Found in rock layers ______________________________________________________
ii. Tropites - a marine _______________________________________________________
iii. Lived between ___________________________________________________________
c. Trilobites
i. Phacops – closest living relative is the ________________________________________
ii. Lived approximately _______________________________
Section Review Questions
1. Explain how an index fossil can be used to date rocks.
2. Explain why the fossil record contains an incomplete record of the history of life on Earth.
3. Explain how fossils can be used to determine the history of changes in the environments and organisms.