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, H 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): Rain Condensation Off gassing of water vapor from volcano

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

Thomas Huxley- Search for origin of life Bathybias heckalii- primordial ooze Wyville Thompson: HMS Challenger ( ) found it was actually diatomacous ooze reacting with seawater and ethyl alcohol Also, disproved Forbes’ Azoic Theory ( )

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

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

chemosynthetic bacteria (extremophiles) Chemosynthesis: H 2 S + C02 CH S +3H 2 0 Stromatolites (bacteria & cyanobacteria) Oldest fossils found in western Australia and southern Africa ~ 3.5 byo Photosynthesis: 6H 2 O + 6CO 2 + nutrients + light energy C 6 H 12 O 6 + 6O 2

Stromatolites from Shark’s Bay Australia mostly cyano

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?