The Solid Earth - Chapter 9: Fossils Flashcards
The branch of geology devoted to the study of ancient life
Paleontology
The remains or traces of organisms preserved from the geologic past
Fossil
What is the clever little one liner about the difference between biology and geology in terms of remains?
If it stinks, it belongs to zoology. If not, to paleontology.
What does it mean when a fossil becomes petrified?
The small internal cavities and pores of the original structures are filled in with precipitated mineral matter (the literal meaning of the term is turned into stone)
If petrification does not occur, what might occur instead? Hint: in this case the cell walls and other solid material are removed and replaced with mineral matter
replacement
Briefly describe replacement
The cell walls and other solid material are removed and replaced with mineral matter
When a shell or other structure is buried in sediment and then dissolved by underground water, a ____ is created
mold
If the hollow spaces are subsequently filled with mineral matter then instead of molds, ___ are created
casts
A type of fossilization called _____ is particularly effective in preserving leaves and delicate animal forms
carbonization
When does carbonization occur?
When fine sediment encases the remains of an organism. As time passes, pressure squeezes out the liquid and gaseous components and leaves behind a thin residue of carbon
True or false: black shales deposited as organic rich mud in oxygen poor environments often contain abundant carbonized remains
True
If the film of carbon is lost from a fossil preserved in fine grained sediment, a replica of the surface called _____ may still show detail
impression
What is a substance that often preserves insects?
Amber
What is amber?
The hardened resin of ancient trees
Why is resin effective for protecting insects?
It seals off the insect from the atmosphere and protects the remains from damage by water and air
What are four types of indirect evidence of life?
Tracks
Burrows
Coprolites
Gastoliths
What are tracks?
Animal footprints made in soft sediment tht was later lithified
What are burrows?
Tubes in sediment, wood, or rock made by an animal. These holes may later become filled with mineral matter and preserved. Some of the oldest known fossils are believed to be worm burrows
What are copolites?
Fossil dung and stomach contents that can provide useful info pertaining to food habits of organisms
What are gastroliths?
highly polished stomach stones that were used in the grinding of food by some extinct reptiles
What are two conditions necessary for fossil formation?
rapid burial
possession of hard parts
What might happen if something is not rapidly buried?
It could be scavenged
Why is our perception of the geologic past due to fossils biased?
Because we only see a tiny glimpse and only of those species that meet the two requirements for fossilization
What did William Smith discover?
That each rock formation in the canals he studied contained fossils unlike those in beds above or below
What is the principle called that indicates fossils represent an order of life?
Principle of Fossil Succession
Geologists pay particular attention to certain fossils called _____ that are widespread geographically and limited to a short span of geologic time
Index fossils
If a clam shell remains are found in limestone, what might the geologist assume?
It was once covered by a shallow sea
