Origin of Life
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Origin of Life. Origin of the Earth. Universe formed 15 billion years ago (Big Bang) Galaxies formed from stars, dust and gas Earth formed 4.6 billion years ago. Origin of the Atmosphere. Suns energy stripped away 1 st atmosphere 2 nd atmosphere formed from volcanic outgassing

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Origin of the Earth

  • Universe formed 15 billion years ago (Big Bang)

  • Galaxies formed from stars, dust and gas

  • Earth formed 4.6 billion years ago

Origin of the Atmosphere

  • Suns energy stripped away 1st atmosphere

  • 2nd atmosphere formed from volcanic outgassing

  • Primitive atmosphere: CO2, water vapor, lesser amts of CO, N2, H2, HCl, and traces of NH3 and CH4(3.5 bya)

Origin of the Atmosphere

  • O2 came in 1.5 bya from photosynthesis

  • Present atmosphere: 78% N2, 21% O2, 0.04% CO2, + trace gasses

Formation of Earth’s Oceans

(4 bybp):

Off gassing of water vapor from volcano



Origin of Life

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

Origin of Life

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

Origin of Life

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

Origin of Life

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

Origin of Life

Thomas Huxley- Search for origin of life

Bathybias heckalii- primordial ooze

Wyville Thompson: HMS Challenger (1872-1876) found it was actually diatomacous ooze reacting with seawater and ethyl alcohol

Also, disproved Forbes’ Azoic Theory (1868-1870)





water vapor



water containing

organic compounds

boiling water

Origin of Life

Miller & Urey (1953)- mixed water vapor, NH3, CH4, H2

+ electric spark  amino acids and other organic compounds

Origin of Life

  • Produced:

  • 20 amino acids

  • Several sugars

  • Lipids

  • Purine and pyrimidine bases (found in DNA, RNA & ATP)

chemosynthetic bacteria (extremophiles)


02 + 4H2S + C02 CH20 + 4S +3H20

Stromatolites (bacteria & cyanobacteria)

Oldest fossils found in western Australia and southern Africa ~ 3.5 byo


6H2O + 6CO2 + nutrients + light energy C6H12O6 + 6O2


mostly cyano

Stromatolites from Shark’s Bay Australia


  • How old is the Earth?

  • What was the 1st organism to have appeared 3.5 bya?

  • How did it eat?

  • When did oxygen 1st appear in the atmosphere?

  • How was it produced?

  • What did Miller & Urey’s study conclude?