Biology 1202 Lecture 2

Biology 1202 Lecture 2 - Biology 1202 Lecture 2 Chapter 25...

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Biology 1202 Lecture 2 Chapter 25 o How did life begin? o A few centuries ago … People thought that new living things appeared all the time 1609 “ There is a tree… frequently observed in Scotland. From this tree leaves are falling; upon one side they strike the water and slowly turn into fishes, upon the other side they strike the land and turn into birds. o Spontaneous Generation Refuted Mid 1800’s Louis Pasteur (broth in flask is boiled to kill preexisting microorganisms). As broth cools, condensing water collects, sealing the mouth of the flask If neck is later broken off, outside air can carry microorganisms into broth o Somehow, life spontaneously generated on the earth, we don’t know why. o Conditions on early earth Atmosphere: Carbion dioxide, methane, ammonia, hydrogen, nitrogen, HCl, HS, water vapor No free oxygen Frequent storms with lots of lightning Frequent volcanic eruptions Frequent meteor impacts UV light from the sun
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Biology 1202 Lecture 2 - Biology 1202 Lecture 2 Chapter 25...

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