Life on Earth has changed dramatically throughout the course of geologic history
- historical record of evolution = fossils
I. Fossils and the Study of Past Life
A. What are fossils?
=> Definition: The remains or trace of organisms preserved from the geologic past........
B. How do fossils form?
=> a very small fraction of organisms that have lived on Earth represented as fossils......Why?
Environmental conditions, chemical recycling, etc.
Requirements for preservation
hard parts
b. rapid burial
Types of preservation...
Typical Fossils
a. Unaltered Skeleton
b.Petrification/Permineralization
- pores filled with silica
- light material becomes much heavier
c. replacement (pyrite and quartz)
- atom for atom replacement
d. molds and casts
- shell dissolved away - mold
- space filled with sediment -cast
* exceptional preservation
- most of organism preserved - including soft parts
1) freezing
2) mummification
3) amber
Types of fossils
1. Body Fossils
- skeletons
2. Chemical Fossils
- chlorophyll
3. Trace Fossils
a) tracks
b) burrows
- records the behavior of organisms
Oddballs
4. Coprolites (“coprolites happen”) and gastroliths
The classification of animals - taxonomy
=> Linnaeus
scheme used for both fossils and living animals
=> are there any differences between fossils and living organisms?
Fossils are classified using skeletal morphology (shape)
Shape Categories:
- Symmetry
- Coiling
Common Fossil Invertebrate Phyla
Porifera
Cnidaria
Brachiopods
Bryozoans
Molluscs
- bivalves
- gastropods
- cephalopods
Arthropods
Echinoderms