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Origin of Life (involves 5 steps leading to life (Involves requirements…
Origin of Life
involves 5 steps leading to life
Liquid water present
Abiotic synthesis of small organic molecules
Monomers packing together to form polymers
Packing polymers
Replication and inheritance
Involves requirements for continuation of life
Cell theory
not applicable to viruses
Energy use and metabolism
Response to environment
not applicable to viruses
Growth and development
Reproduction
Biological evolution
Environmental characteristics needed to support life
Temperature
pH
Oxygen level
Atmospheric pressure
Salt concentration
concepts supported by evidence such as
Miller-Urey Experiment
closed system set up with water source and mixtures of gases
inorganic components formed building blocks (amino acids)
John Sutherland experiment
experimented with abiotic synthesis of DNA and RNA
scientist
Comets
shock synthesis idea supported idea of monomer formation to polymer
Surface molecules interaction
RNA nucleotides interact with montmorillonite clay resulting in polymer formation
Catalytic nature of RNA
ability to cut other pieces and active themselves led to ideas of RNA interaction in cells
RNA can be made in abiotic environment
RNA world hypothesis
concept that earliest forms of life had RNA based genomes
switched to DNA based genome through chemical selection
Self replication
RNA replicase makes RNA from template of RNA
involves environment conditions in Earth
The Great Oxygenation Event
free oxygen becomes present on Earth 2.7 bilion years ago
oxygenic photosynthesis of cyanobacteria led to change in environment
anaerobic organisms now at disadvantage
Earth went from reducing to oxidizing environment
comes with trade-offs
Oxygen is toxic to most early organisms
supports combustion
implicit in aging and cancer
free radical can cause damage to DNA, proteins, lipids
resulted in mass extinction event as life became aerobic
Organisms generating more ATP use oxygen as final electron acceptor
Organisms can grow faster
Life began in water environments
order of events shown in geologic record
aquatic organisms before land organisms
involves when life began
Evidence found from 3.7 billion years ago
first cells evolved between 3.7 and 3.8 billion years ago
liquid water present 3.8 billion years ago
first fossils found 3.7 billion years ago
formed from stromatolites
involves where life began
Hydrothermal vents found in deep sea