ASTRON 1F03 Chapter 18: Chapter 18
12 Apr 2016
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Document Summary
Difficult to define but there are some generally agreed-upon characteristics that any life form should have: Ability to grow by taking in nourishment and processing it into energy. Ability to reproduce with offspring having characteristics of parent. The history of the universe is one of increasing complexity marked by several stages leading eventually to intelligent life. We have very little information about the first billion years of earth"s existence; Earth was simply too active at that time. It is believed that there were t=many volcanoes and an atmosphere of hydrogen, nitrogen, and carbon compounds. As earth cooled, methane, ammonia, carbon dioxide, and water formed. Earth was subject to volcanoes, lightning, radioactivity, ultraviolet radiation, and meteoroid impacts. Over ~gyr, amino acids and nucleotide bases, the basis of dna, formed. The process by which this happens has been recreated in the laboratory. Protein-like droplets created form clusters of billions of amino acid molecules.
