BIOL 1202 Chapter : Ch 25
Document Summary
Chapter 25: the history of life on earth. Earth is about 4. 6 billion years old: formed by radiometric dating of meteorites & moon rocks. Life arose about 3. 8 billion years ago: chemical traces in rocks 3. 8 by, fossil bacteria in rocks 3. 5 by. No spontaneous generation now, but must have happened then. Atmosphere: co2, ch4, nh3, h2s, h2o, today it"s mostly nitrogen and oxygen, no free oxygen. Abundant energy to drive reactions: frequent storms with much lightening, frequent volcanic eruptions, frequent meteor impacts, uv light from the sun. Testable hypothesis explaining the origin of life. First organic compounds may have been synthesized near hydrothermal vents. Small organic molecules polymerize when they are concentrated on hot sand or clay. Accumulations of abiotically produced molecules surrounded by a membrane. Liposomes can form when lipids or other organic molecules are added to water. Now: dna rna protein, need proteins to synthesize more dna.
