BIOL 1201 Chapter : How Did Life Begin
Document Summary
Hypothesis leads to observations which lead to explanations. Darwin explained how life begin on this planet. People thought new living things appeared all the time. In the early 1600s, people had a more poetic view of life and the way it began. Mid 1800s louis pasteur expressed his ideas. Broth in flask boiled to kill preexisting microorganisms. Broth cools, condensing water collects, sealing the mouth of the flask. If the neck is later broken off, outside air can carry microorganisms into broth. Atmosphere: there is approximately 20% oxygen in the air today; photosynthesis hadn"t yet evolved and created more oxygen energy. Radiometric dating of meteorites and moon rocks. Life arose 3. 8 billion years ago as soon as water was on earth. Chemical traces in rocks are 3. 8 billion years old. Fossil bacteria in rocks are 3. 5 billion years old. There is no proof of spontaneous generation now, but it must have happened then: all existing cells come from preexisting cells.
