Presentation on theme: "CHAPTER 25 ORIGIN OF LIFE ON EARTH Past organisms were very different from those now alive The fossil record shows macroevolutionary changes over large."— Presentation transcript:
So where did the first organic molecules come from? Miller-Urey and others demonstrated that organic materials can be produced from inorganic molecules under certain circumstances.
MILLER-UREY EXPERIMENT Conditions of Early Atmosphere of Earth Before Life Products of Experiment Flask with H, methane, ammonia, H 2 0 (no free oxygen! O 2 ) Spark (to represent lightning) Some amino acids, and cytosine and uracil
Figure 25.2a Mass of amino acids (mg) Number of amino acids Under Volcanic Conditions (green) the results were even more notable than the original experiment (orange)
Which came first? DNA, RNA, or Protein DNA first- Probably not. What does DNA require in order to replicate? RNA first Not only can RNA replicate, but it can sometimes act like an enzyme (ribozyme). Protein first Not only can proteins perform countless functions, but they can also replicate (prions).
Dimetrodon Stromatolites Fossilized stromatolite Coccosteus cuspidatus 4.5 cm 0.5 m 2.5 cm Present Rhomaleosaurus victor Tiktaalik Hallucigenia Dickinsonia costata Tappania 1 cm 1 m 100 mya ,500 3, Figure 25.4 Stromatolite fossils are the remains of prokaryotes