1. How did life on Earth begin? Spontaneous generation-life from non lifeSpontaneous generation-life from non life Search for truth 1. Redi 1668 2. Needham 1745 3. Spallanzani 1770 Air contained “active principle” 4. Pasteur 1864 - boil broth - straight vs curved next open flasks biogenesis - support biogenesis- life from life

2. If life comes from life, then how did life on Earth first arise? Earth 4.6 bya Big Bang Volcanism large role in formation of atmosphere and oceans Methane, ammonia, water, carbon dioxide, nitrogen, and hydrogen

3. Chemical Evolution Oparin Hypothesis 1924 - chemical reactions between molecules w/o O 2 Miller and Urey 1953 - test Oparin’s hypothesis - added electrical spark - got “primordial soup”, formation of organic molecules amino acids, sugars, and nucleotides Additional experiments indicate RNA may be life’s 1 st code

4. Miller’s Products Miller’s Experiment

5. Alternate Theories Meteorite 1969 Deep Ocean Vents

6. What were the first cells like? Prokaryotic Anaerobic Heterotrophs Over a period of time, cells became autotrophic chemosynthesizers Set the stage for photosynthesis How was the atmosphere changed?

7. Unicellular to multicellular? How did that happen? Formation of ozone layer Ability to perform aerobic respiration Lynn Margulis “endosymbioant theory” - ancestors to today’s eukaryotic cells preyed upon other microbes Sexual reproduction- genetic variation new species