Earth is estimated to be ~4.6 bill. yr old –Evidence: Radiometric dating of rocks & meteors Nebula Hypothesis: –Nebula: cloud of gas & dust in space –Gravity pulled much material together (forming the Sun) –Planets formed from remaining materials

What was it like? Atmosphere contents: –Ammonia, H 2 O vapor, Methane (CH 4 ), CO 2 Climate: –Extreme heat due to meteor impacts & volcanic activity Eventually Cooling: Water vapor condensed (oceans formed) Click on picture to play video clip

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 were created 1. Miller - Urey Experiment

2. Meteorite Hypothesis Hypothesis: Amino acids may have arrived on Earth through meteorite or asteroid impacts. Fun Fact! 90 amino acids were found from this meteorite, only 19 of them can be found on Earth.

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

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. – Because of this, scientists think that DNA evolved from RNA

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

Evolution of sexual reproduction led to increased diversity/variation. Sexual reproduction may have led to multicellular life.

Review These are questions that I would ask you on the test, so you should do your best at answering them accurately and completely. What is a nebula? What does the nebula hypothesis try to explain? What materials/ingredients did Miller & Urey use in their experiment? Why these and not other ingredients? Why was Miller and Urey’s experiment of great importance? How did eukaryotic cells form? How would sexual reproduction lead to diversity and multicellular life?