HL A2.1 The Origin of Life On Earth
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What conditions existed on early Earth that allowed life to begin?
Early Earth had a reducing atmosphere with methane, carbon dioxide, ammonia, and hydrogen, no free oxygen or ozone, high temperatures, UV radiation, and energy from lightning and volcanism, allowing organic molecules to form.
What is meant by a reducing atmosphere?
An atmosphere lacking oxygen where electrons are easily donated, favouring the formation of complex organic molecules.
What sequence of events is proposed for the origin of life?
Inorganic molecules → simple organic molecules → complex polymers → self-replicating molecules → protocells → first cells.
What is the primordial soup hypothesis?
Organic molecules accumulated in early oceans and reacted to form larger biological molecules.
What energy sources drove early chemical reactions?
Lightning, UV radiation, geothermal heat, and volcanic activity.