Origin of Life

Origin of the Solar System Earth is estimated to be ~4.6byo –Radiometric dating of rocks & meteors Nebula: cloud of gas & dust in space Nebula Hypothesis: –Gravity pulled much material together (Sun formed) –Planets: remaining materials

Ancient Earth Atmosphere contents: –Ammonia, H 2 O vapor, Methane, H 2, Climate: –Extreme heat due to meteor impacts & volcanic activity Eventually Cooling: Water vapor condensed (oceans formed) Click on picture to play video clip

Where did organic molecules come from?

Hypothesis: Energy from lightning created organic materials from inorganic ingredients Experimental Set-Up: –Ammonia, H 2 O vapor, Methane, CO gases added –Electricity added (simulate lightning) Result: Amino Acids & later nucleotides

Murchison Meteorite

Cell Formation? Lipid membrane hypothesis Liposomes –Spheres of lipids –Can form around organic molecules –Hypothesis: 1 st cell membranes?

RNA as Early Genetic Material A hypothesis proposes that RNA was the first genetic material. –Ribozymes are RNA molecules that catalyze their own replication. –DNA needs enzymes to replicate itself.

What about eukaryotic cells? How did they form?

Eukaryotic cells may have evolved through endosymbiosis. Endosymbiosis is a relationship in which one organism lives within the body of another. Mitochondria and chloroplasts may have developed through endosymbiosis.