Q.Prepare a diagrammatic chart of the chemical evolution of life.

The chart should trace the Oparin-Haldane sequence of section 5.2 as a downward flow: origin of the Earth and its reducing primitive atmosphere, formation of ammonia, water and methane, formation of simple organic molecules in the hot dilute soup, polymerisation into complex organic molecules, formation of nucleic acids, protobionts (coacervates and microspheres), and finally the first anaerobic heterotrophic cell, with the Urey-Miller experiment placed beside the step it supports. …

Aim. To present the self-assembly (Oparin-Haldane) theory of the origin of life as one diagrammatic chart.

Layout to draw. Seven boxes in a vertical or spiral flow, joined by arrows, each with a one-line note:

1. Origin of Earth and primitive atmosphere (about 4.6 billion years ago) - a hot nebula cools; heavy elements sink to the core; hydrogen, helium, nitrogen, oxygen and carbon form a reducing atmosphere with no free oxygen.
2. Formation of ammonia, water and methane - as the hot atmosphere cools, reactive hydrogen combines with carbon, nitrogen and sulphur to give CH4, NH3, H2O and H2S.
3. Formation of simple organic molecules - steam condenses, rain fills the seas; ultraviolet rays, lightning and volcanic energy drive condensation, polymerisation, oxidation and reduction, giving monosaccharides, amino acids, purines, pyrimidines, fatty acids and glycerol that collect as Haldane's 'hot dilute soup'.
4. Formation of complex organic molecules - polymerisation in the neutral, oxygen-free broth gives polysaccharides, fats, protoproteins and proteins (the first enzymes), nucleosides and nucleotides.
5. Formation of nucleic acids - nucleotides join into RNA and DNA, which acquire the self-replicating ability fundamental to life.
6. Formation of protobionts (procells) - nucleic acids with organic and inorganic molecules aggregate into coacervates (Oparin) and microspheres (Sidney Fox), which grow and divide but are still non-living.
7. Formation of the first cell - an RNA/DNA system inside a protocell regulates metabolism; the first cell is anaerobic and chemoheterotrophic. …