PALEOBIOLOGY

• The discipline of geology that studies ancient forms of life, their interactions, and their evolution.
• FOSSILIZATION
• Involves the transferral of an organism from the biosphere to the lithosphere.
• May be a result of death, part loss, or reproductive dissemination.
• PROCESSES TOWARDS FOSSILIZATION
• Most organic remains composed of labile chemicals (easily degraded) and, hence, are not prone to preservation.
• Mineralized skeletal elements enhance the probability of preservation.
• Aragonitic shells possess an unstable crystallinity, often recrystallize into calcite.
• May be enhanced by pore water circulation of dissolved silica, CaCO3, or iron resulting in precipitation within the pore spaces.
• ROLE OF ORIGINAL BIOCHEMISTRY
• Specific biochemicals are more prone to preservation than others.
• For example, in terrestrial plants:
• Plant cuticles
• Spores & pollen
• Wood - lignin
• POTENTIAL FOR FOSSILIZATION
• High sedimentation rates accompanied by reducing (oxygenless) geochemical conditions increase the probability of preservation.
• Open marine environments (below wave base) possess the highest potential for preservation of biotic components.
• Aerially exposed environments (landscapes) possess the lowest potential for preservation of biotic components.
• HOW COMPLETE IS THE FOSSIL RECORD?
• Because of taphonomic biases, the fossil record is incomplete.
• But, in spite of this fact, it is remarkably comprehensive.
• CLASSIFICATION OF FOSSIL ORGANISMS
• Fossils are classified according to the biological system of nomenclature established by Linnaeus
• Classification is based on morphological features.
• Binomial classification - Genus and species
• SPECIES CONCEPTS IN BIOLOGY AND PALEOBIOLOGY
• Biological species - Population or group of populations in which individuals can interbreed.
• Paleontological species - A population of fossils that exhibits the same range in morphological/ anatomical characters.
• Fossils and Stratigraphy
• Speciation (organic Evolution) occurs rapidly around the globe
• Successful taxa radiate into climatic belts in which they can survive.
• Rocks formed during the same age in identical depositional environments and diverse localities often contain similar biota.
• Therefore, possible to match chronologically and/or correlate strata.
• Fossils and Stratigraphy
• Geologic range of biota within each chronostratigraphic (time-rock) unit.
• Oldest (origination) and youngest (extinction) occurrence stratigraphically.
• More Fossils and Stratigraphy
• Stratigraphic range determined only by recording occurrences in many stratigraphic sequences from many localities.
• Fossils & Stratigraphy
• Paleontological correlation is not made utilizing a single fossil species
• Even MORE Fossils and Stratigraphy
• Changes in ranges of a taxon in different parts of the globe may not reflect evolution, but may indicate biotic migration or shifts in response to climatic change.
• Most resistant fossils (biochemically stable forms) may be reworked (weathered and eroded from exposed rock and redeposited in another time period).
• Guide Fossils
• Guide fossils -ancient organisms that are abundant and widespread, but lived during a relatively short period of Earth history (MY).
• Useful in identifying chronostratigraphic (time- rock) units.
• Guide fossils reflect a fast evolutionary rate; that is a rapid change in form in short intervals of time.
• BIOZONES
• Biozones -when a body of rock is identified on the fossil assemblage it preserves.
• A biozone may be based upon the range of a specific group of organisms - Range Zone.
• A biozone may be based upon the ranges of coexisting taxa -Assemblage zone.

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