How did non-living chemicals become living creatures? What does it mean to be alive? What does it mean to be alive? Energy from chemical reactions can assist in other chemical reactions Energy from chemical reactions can assist in other chemical reactions –Precursor to “eating” Some chemicals catalyze other chemical reactions Some chemicals catalyze other chemical reactions –Precursor to protein synthesis and metabolism? Some chemicals are capable of self-replication Some chemicals are capable of self-replication –Precursor to reproduction?

Possible Sites for the Origin of Life Clay Clay –Mineral structure acted as template for organic material Pyrite Pyrite –Mineral structure acted as template for organic material Bubbles Bubbles –separation of chemical environments within and without Tidal Pools Tidal Pools –separation of chemical environments within and without Hot springs/Hydrothermal Vents Hot springs/Hydrothermal Vents

A New Hypothesis Life may have originated near hot springs and volcanic vents Life may have originated near hot springs and volcanic vents Heat supplied the energy for life processes Heat supplied the energy for life processes Energy also available from chemical reactions Energy also available from chemical reactions Entire ecosystems without a basis in sunlight! Entire ecosystems without a basis in sunlight!

Organisms around a modern black smoker vent

Evidence Genetic mapping of living bacteria Genetic mapping of living bacteria “Oldest” groups are Thermophiles “Oldest” groups are Thermophiles –Hot Springs –Volcanic vents on sea floor Fossil evidence has not been found – yet Fossil evidence has not been found – yet Such settings are not likely to be preserved in the rock record – sea floor is subducted! Such settings are not likely to be preserved in the rock record – sea floor is subducted!

Earliest Fossils: Prokaryotes Prokaryotes – cells with no nucleus Prokaryotes – cells with no nucleus –Mostly cyanobacteria (formerly blue-green algae) Single cells Single cells Strings of cells Strings of cells Mats of cells – Stromatolites Mats of cells – Stromatolites –Structures built as mats trap and bind sediment

Cyanobacteria – 3.46 Ga

Stromatolites - Modern and Ancient Shark Bay, Australia Saratoga Springs, NY

Extraterrestrial Origins of Life? Ingredients in comets Ingredients in comets Evidence from meteorites Evidence from meteorites Could life have been transplanted to Earth from an extraterrestrial source? Could life have been transplanted to Earth from an extraterrestrial source? Did life arise on Earth and other planets simultaneously? Did life arise on Earth and other planets simultaneously?

Magnetite from Martian Meteorite – evidence of bacteria?

The Allan Hills Meteorite Bacteria(?) from Mars

Life in Stasis: 3 Ga of Single Cells Life begins – approximately 4.0 Ga Life begins – approximately 4.0 Ga 3.8 Ga – first stromatolites 3.8 Ga – first stromatolites 3.46 Ga – preserved filaments of cyanobacteria 3.46 Ga – preserved filaments of cyanobacteria Ga – at least 12 species of prokaryotes Ga – at least 12 species of prokaryotes 1.0 Ga – first eukaryotes 1.0 Ga – first eukaryotes 0.9 Ga (900 Ma) – sexual reproduction 0.9 Ga (900 Ma) – sexual reproduction 600 Ma – first multicellular organisms 600 Ma – first multicellular organisms

The Ediacaran Biota Earliest Multicellular Life