Earth’s Atmosphere & The Origin of Life

Stages of Earth’s Atmosphere

• Reducing Atmosphere• Neutral Atmosphere• Oxidizing Atmosphere

Reducing Atmosphere

• Major GasesHydrogen (very reactive) and

subsequently Methane, Ammonia, Hydrogen Sulfide, and Water Vapor

Important Reactions

• H2 + Oxygen Comp. Water

• H2 + Nitrogen Comp. Ammonia (NH3)

• H2 + Carbon Comp. Methane (CH4)

• H2 + Sulfur Comp. Hydrogen Sulfide (H2S)

Stanley Miller’s Experiment

Origin of Organic Molecules

• Stanley Miller demonstrated that Earth’s earliest atmosphere could produce some organic molecules arise from inorganic substances

• Organic Molecules are complex compounds that contain Carbon and Hydrogen atoms

Neutral Atmosphere

• Major GasesNitrogen, Carbon Dioxide, and Ozone

Important Reactions

• PhotodissociationH2O with UV radiation H2 + O2

Oxygen Gas Ozone (O3)

• Reactions involving OxygenO2 + NH3 Nitrogen Gas (N2) + H20

O2 + CH4 Carbon Dioxide (CO2) + H20

(Greenhouse Effect)

Origin of Life

The Cell

• The cell is a place where chemical reactions occur.

• The container is composed of phospholipids having hydrophilic heads and hydrophobic tails.

Oxidizing Atmosphere

• Major GasesNitrogen, Carbon Dioxide, Oxygen,

Ozone

• Evolution of Eukaryotic Cells

Endosymbiont Hypothesis

Eukaryotic cells containing

a nucleus and membranebound organelles

(Chloroplasts and

Mitochondria) are believed

to have arisen from

Prokaryotes thatincorporated other

Prokaryotes.