BIOL 1202 Chapter : Chapter 25 The History Of Life On Earth
Document Summary
Earth is about 4. 6 billion years old (by: radiometric dating of meteorites and moon rocks. Life arose about 3. 8 by ago: chemical traces in rocks 3. 8 by, fossil bacteria in rocks 3. 8 by. No spontaneous generation now, but must have happened then. Atmosphere: co2; ch4; nh3; h2s; h2o, no free oxygen. Abundant energy to drive reactions: frequent storms w/ much lightening, frequent volcanic eruptions, frequent meteor impacts, uv light from the sun. Testable hypotheses explaining the origin of life. Organic molecules appear after only a few days. First organic compounds may have been synthesized near hydrothermal vents(volcanic hot springs, bottom of the ocean, brings a lot of reduced compounds to the sea water, forming simple organic molecules) Extraterrestrial origin (organic compounds came in on meteorites, comets) Small organic molecules polymerize when they are concentrated on hot sand or clay: adenines bind to clay template rate of dehydration synthesis exceeds the rate of hydrolysis adenines link through sugar-phosphate bonds.
