Origin of life Donald Winslow, 1 April 2014 Reference: What is Life: A guide to Biology, 2 nd edition by Phelan (2013). W. H. Freeman and Co. ISBN (13): ISBN (10): Chapter 10, pp

Origin of life Earliest origins not well understood Complex organic molecules Cells Self-replicating systems

Atmospheric conditions before life Almost no oxygen in atmosphere Volcanoes contributed simple compounds CO 2, N 2, CH 4, NH 3, H 2, H 2 S 2

Phases of life's origin Phase 1—Small compounds with C & H Phase 2—Self-replicating molecules Containing information Phase 3—Development of membrane Enabling metabolism First cells

Small organic molecules Miller and Urey (1953) Flask with H 2 O, H 2, CH 4, and NH 3 Sparks to simulate lightning Cooled so that water would condense & fall Produced all 20 amino acids found in cells!

Self-replicating molecules RNA world? DNA world? Protein world? Self-replicating systems with all three

First cells 3.4 billion year old prokaryote fossils Microspheres form from phospholipids Membrane Protects large molecules from outside