Chapter 17. The origins of life and Precambrian evolution

EVOLUTION/LECTURE1
7.2.- Miller used methane, ammonia, and hydrogen as in the 1950s it was thought that
the atmosphere of the young Earth was highly reducing. However, many atmospheric
chemists now believe that Earth's early atmosphere was not so reducing, being dominated
by Carbon Dioxide rather than methane, and molecular nitrogen rather than ammonia.
7.3.- Reaching a consensus on the prebiotic environment is important, because an
atmosphere dominated by carbon dioxide and molecular nitrogen appears to be
much less conducive to the formation of certain organic molecules.
7.4.- The view that the Earth possessed all the necessary ingredients for the origin
of life is perhaps the most thoroughly investigated hypothesis and holds great
appeal for many scientists even today. This opinion dates back to the efforts of
A. Oparin and J.B.S. Haldane, working in the first half of the 20th century. This
scenario is often referred to as the Oparin-Haldane model
8.- From simple inorganic to the building blocks of life
8.1.- Previously, we saw the ease with which amino acids can be made from simple
inorganic like methane, ammonia, and hydrogen. What about nucleotides. A
second monumental achievement in origins-of-life research was the demonstration
by Juan Oró (1961) that the nitrogenous base adenine (a purine) could be readily
made from a thermodynamically favorable reaction involving only ammonia
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