Unit 10: Origin and History of Life
Hypothesis on the Origin of Life
• The production of simple cells
–Abiotic synthesis of small organic
molecules
–Macromolecules
–Protocells
–Self-replicating molecules
Abiotic Synthesis of Organic Polymers
• Oparin and Haldane
– Early Earth
• Reducing atmosphere
• Energy
• Miller and Urey
– Primordial environment
• Formed organic
compounds
Other Supporting Evidence
• Abiotic synthesis of macromolecules
– 2009 study
• Protocells
– Vesicles
• Self-replicating RNA
– Ribozymes
– RNA world
How Life May Have Emerged
• Volcanoes released gases
– Atmosphere formed
• Gases condensed
• Organic molecules
– Energy
– Joining of inorganic molecules
• Polymers and self-replicating molecules
– Dehydration reactions
How Life May Have Emerged
• Protobionts
– Unable to reproduce
– Can carry out chemical reactions
• Heterotrophic prokaryotes
– Limited recources
– Anaerobic
• Autotrophic prokaryotes
– Mutations
How Life May Have Emerged
• Oxygen and ozone
– Product of photosynthesis
• Eukaryotes appeared
– Symbiotic relationships
• Life evolved
– Natural selection
Geologic Time Scale
Endosymbiotic Theory
Fossil Evidence for the History of Life
• See textbook on page 511, Figure 25.4
Continental Drift
Mass Extinctions
• 5 major mass extinctions
– Permian
• Pangaea
• 96% loss of marine animal species
– Cretaceous
• Volcanic eruptions in Siberia
• Global warming and drop in oxygen
• Loss of 50% marine and many terrestrial plant and
animal families, including dinosaurs
The 6th Mass Extinction
• Human Impact
– Habitat destruction
– Industrialization
• Recovery
– 5 to 10 million years
Phylogenic System of Classification
• Previous Systems
– 5 kingdom system
– 6 Kingdom system
• Current System
– 3 domain system
Three Domain System
Three Domain System
• Characteristics of the universal ancestor
• Different conclusions
• Evidence
Adaptive Radiation
Reproductive Barriers