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

- support biogenesisbiogenesis- life from life

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

Chemical EvolutionChemical Evolution• Oparin Hypothesis 1924

- chemical reactions between molecules w/o O2

• 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 1st code

Miller’s Products

Miller’s Experiment

Alternate TheoriesAlternate Theories

• Meteorite 1969

• Deep Ocean Vents

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?

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