Archean Life
• oldest fossil = 3.5 g.a., but life began 3.8 g.a.
• What is life?
– Metabolism/Reproduction
Origin of Life
• Self replication and regulation - amino acids
• Miller & Urey experiment - amino acids
• Requirements
- Appropriate elements
- Energy source
• prebiotic stage- microspheres (Fox)
• Need complex organic polymers
• Templates - clays or pyrite
Earliest Organisms
• autotrophic prokaryotes
• Anaerobic
• Environments
– Shallow marine
– Hydrothermal Vents (chemotrophs)Early Proterozoic Life
• Very little change in the types of life on Earth occur at the boundary
between the Archean and the Proterozoic
• more cyanobacteria and eukaryotic algae
• Stromatolites - more abundant and diverse than any other time
– => decrease abruptly - Phanerozoic -Why?
Early Eukaryotes
• first eukaryotes = Archean?, but fist appearance as fossils = Proterozoic
• How did eukaryotes evolve from prokaryotes
– clues - RNA and DNA from organelles
– symbiotic relationship or consumed
– smaller cell becomes mitochondrion- animal-like
– plant like - chloroplast
The Neoproterozoic/Vendian (1 billion - 560 milion)
• The diversification of life - Metazoans
• Trace Fossils
• Ediacaran Fossils - Cnidaria - imprints
• Skeletal Fossils - unknown group
What triggered the diversification of Life?
• levels of O2 in the atmosphere high enough to support Metazoans?
• Nutrients
• The “salad bar”
• More complex ecology
– tiering
The Cambrian Explosion
• The Cambrian Explosion - Early Cambrian Life
• first record of abundant life
• variety of marine life with skeletons
• most phyla of marine organisms appear
• WHY THE SUDDEN APPEARANCE OF FOSSILS???
– Innovation = a skeleton
The Cambrian Explosion
• Discuss the following question with the people around you:
• Why would having a shell be important?
Cambrian Life
• Large Animals with Skeletons
• the Trilobites => “Age of the Trilobite”
• other arthropods = anomalocarids
• why a skeleton might be important!
Cambrian Life
• The Cambrian Fauna
• Trilobites
• Archaeocyathids
• Brachiopods
• Molluscs
Cambrian Life
• A “snapshot” of Cambrian life - Burgess Shale assemblage
• A “lagerstätten”
– Soft-bodied fossils preserved - the whole community
• Experiments in form - soon became extinct