BIOL 1010 Lecture Notes - Lysosome, Endoplasmic Reticulum, Cell Membrane
Document Summary
Milestones in the history of life on earth (table 25. 1) Chapter 25: the earth is believed to be 4. 6 billion years old, all life can be traced back to primeval prokaryotes that lived 3. 5 to 3. 9 billion years ago. Prokaryotes dominated earth from 3. 5 to 2 billion years ago. Oldest fossils = stromatolites 3. 5 billion years: o2 accumulation in the atmosphere - 2. 7 billion years ago. There was little atmospheric oxygen on early earth. The atmosphere likely contained water vapour, co2, methane, ammonia, hydrogen, h2s, and nitrogen and its oxides. It may or may not have been reducing and there most likely were small regions (e. g. , around volcanic vents) that were definitely reducing (favourable for synthesis of organic molecules). As the earth cooled the water vapour condensed into oceans and much of the hydrogen escaped into space. Experiments attempting to mimic conditions on primitive earth supported the formation of complex organic molecules (e. g. , amino acids, nitrogenous bases).
