Universe formed 15 billion years ago Big Bang

• Universe formed 15 billion years ago (Big Bang) • Galaxies formed from stars, dust and gas • Earth formed 4. 6 billion years ago

• Suns energy stripped away 1 st atmosphere • 2 nd atmosphere formed from volcanic outgassing • Primitive atmosphere: CO 2, water vapor, lesser amts of CO, N 2, HCl, and traces of NH 3 and CH 4 (3. 5 bya)

• O 2 came in 1. 5 bya from photosynthesis • Present atmosphere: 78% N 2, 21% O 2, 0. 04% CO 2, + trace gasses

Formation of Earth’s Oceans (4 bybp): Off gassing of water vapor from volcano Condensation Rain

Life began~ 3. 5 bya Organic molecules (C H O N P S) swimming in shallow seas Stage 1: Abiotic synthesis of organic molecules such as proteins, amino acids and nucleotides

Stage 2: joining of small molecules (monomers) into large molecules

Stage 3: origin of self-replicating molecules that eventually made inheritance possible

Stage 4: packaging these molecules into pre-cells, droplets of molecules with membranes that maintained an internal chemistry

Miller & Urey (1953)- mixed water vapor, NH 3, CH 4, H 2 + electric spark amino acids and other organic compounds electrodes CH 4 NH 3 H 2 water vapor spark condenser boiling water containing organic compounds

Produced: • 20 amino acids • Several sugars • Lipids • Purine and pyrimidine bases (found in DNA, RNA & ATP)

chemosynthetic bacteria (extremophiles) Chemosynthesis: 02 + 4 H 2 S + C 02 CH 20 + 4 S +3 H 20 Stromatolites (bacteria & cyanobacteria) Oldest fossils found in western Australia and southern Africa ~ 3. 5 byo Photosynthesis: 6 H 2 O + 6 CO 2 + nutrients + light energy C 6 H 12 O 6 + 6 O 2

mostly cyano Stromatolites from Shark’s Bay Australia

Inquiry 1. How old is the Earth? 2. What was the 1 st organism to have appeared 3. 5 bya? 3. How did it eat? 4. When did oxygen 1 st appear in the atmosphere? 5. How was it produced? 6. What did Miller & Urey’s study conclude?