Earth’s Atmosphere & The Origin of Life

Stages of Earth’s Atmosphere Reducing Atmosphere Neutral Atmosphere Oxidizing Atmosphere

Reducing Atmosphere Major Gases Hydrogen (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 Gases Nitrogen, Carbon Dioxide, and Ozone

Important Reactions Photodissociation Reactions involving Oxygen H2O with UV radiation  H2 + O2 Oxygen Gas  Ozone (O3) Reactions involving Oxygen O2 + 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 Gases Evolution of Eukaryotic Cells Nitrogen, Carbon Dioxide, Oxygen, Ozone Evolution of Eukaryotic Cells

Endosymbiont Hypothesis Eukaryotic cells containing a nucleus and membrane bound organelles (Chloroplasts and Mitochondria) are believed to have arisen from Prokaryotes that incorporated other Prokaryotes.