HOW DID LIFE GET HERE?

1. Direct evidence: Fossilised chains of bacteria-like cells found in Marble Bar W.A. Occur in rocks dated at 3500 Myr ago HOW DID LIFE GET HERE? Still being debated as possible these structures were produced by geological action NOT biological First signs of life?

2. Earth 3,500 Million Years Ago Anoxic atmosphere: Nitrogen, carbon dioxide, methane, ammonia, sulphur dioxide and hydrogen sulphide Extreme UV radiation: No ozone Extreme weather conditions: Water cycle Extreme geological activity: Volcanoes, earthquakes

3. What is needed for life? Liquid water: Provides medium for reactions to occur and an essential solvent. Usable energy source: Needed for all life’s functions. The chemicals that make up all life Organic molecules: Two Hypotheses 1. Organic molecules produced on early Earth Aleksandr Oparin and J.B.S. Haldane suggested that the organic molecules needed for life were produced under the conditions on early Earth. (1920’s) In the 1950’s Stanley Miller and Harold Urey set up a MODEL of early Earth to test Oparin and Haldane’s hypothesis.

4. Sparks, electrical discharge Lightning in storms Gases, CH4, NH3, H2O, H2 Gases found in Early Earth atmosphere Condenser Water vapour due to water cycle Vacuum Boiling water Water in newly formed oceans 1 week later: Organic molecules found in the water Showed that organic matter can be produced from inorganic material.

5. 2. Organic molecules arrived from space. 1969 – meteorite found in Victoria contained amino acids Confirms organic molecules can be formed outside Earth Early Earth was constantly bombarded with meteorites due to developing Solar System Supports the idea that organic molecules arrived from space. 2001 – NASA replicated in the laboratory conditions that exist in interstellar clouds in space Water mixed with inorganic chemicals, NH3, CO, CO2, CH3OH Freeze to absolute zero in a vacuum Expose to shortwave UV radiation Results: Complex organic molecules