Download Volcanoes and the Origin of Life

How did non-living chemicals
become living creatures?
• What does it mean to be alive?
• Energy from chemical reactions can assist in
other chemical reactions
– Precursor to “eating”
• Some chemicals catalyze other chemical
reactions
– Precursor to protein synthesis and metabolism?
• Some chemicals are capable of self-replication
– Precursor to reproduction?
Possible Sites for the Origin of Life
• Clay
– Mineral structure acted as template for organic
material
• Pyrite
– Mineral structure acted as template for organic
material
• Bubbles
– separation of chemical environments within and
without
• Tidal Pools
– separation of chemical environments within and
without
• Hot springs/Hydrothermal Vents
A New Hypothesis
• Life may have originated near hot springs
and volcanic vents
• Heat supplied the energy for life processes
• Energy also available from chemical
reactions
• Entire ecosystems without a basis in
sunlight!
Organisms around a modern
black smoker vent
Evidence
• Genetic mapping of living bacteria
• “Oldest” groups are Thermophiles
– Hot Springs
– Volcanic vents on sea floor
• Fossil evidence has not been found – yet
• Such settings are not likely to be
preserved in the rock record – sea floor is
subducted!
Earliest Fossils: Prokaryotes
• Prokaryotes – cells with no nucleus
– Mostly cyanobacteria (formerly blue-green algae)
• Single cells
• Strings of cells
• Mats of cells – Stromatolites
– Structures built as mats trap and bind sediment
Cyanobacteria – 3.46 Ga
Stromatolites - Modern and Ancient
Saratoga Springs, NY
Shark Bay, Australia
Extraterrestrial Origins of Life?
• Ingredients in comets
• Evidence from meteorites
• Could life have been transplanted to Earth
from an extraterrestrial source?
• 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
• 3.8 Ga – first stromatolites
• 3.46 Ga – preserved filaments of
cyanobacteria
• 1.9-1.7 Ga – at least 12 species of prokaryotes
• 1.0 Ga – first eukaryotes
• 0.9 Ga (900 Ma) – sexual reproduction
• 600 Ma – first multicellular organisms
The Ediacaran Biota
Earliest Multicellular Life