Theories On How Cellular Life Began Essential Question: Name the theories that describe how cellular life began. One Level 2 Oparin-Haldane Hypothesis – also known as “primordial ______________” Question States that Earth’s early atmosphere didn’t have __________________. It was made of nitrogen, hydrogen, and other compounds, including water vapor. ________________ reacted and oxidized the atoms to form organic compounds. Miller/Urey Experiment tested this theory and simulated the early atmosphere and sent a continuous electrical current through it in the lab. It did create small amounts of organic compounds, like amino acids. Scientists are skeptical because there were probably not enough lightning storms to create all the molecules needed for life. Iron-Sulfur World Theory- life began on the surfaces of mineral deposits near ___________________ vents on the ocean floor. Carbon reacted with those minerals, like iron and sulfur, to create organic compounds like carbon dioxide. Under high pressure and temperature, the chemical reactions underwater would create molecules needed for metabolism. This theory can’t explain how life duplicates itself. RNA World Hypothesis – RNA can act as a catalyst (jumpstart) to drive chemical reactions necessary for life. Proposes RNA existed before ___________. This explains how simple molecules could become complex self-replicating systems. We still don’t know how RNA was formed and there is much debate on this theory. Endosymbiotic Theory – 1960s, it was noted that mitochondria and chloroplasts have a lot more in common with prokaryotes than eukaryotes. It is thought that these organelles might have once been free-living bacteria because they have their own ________. These cells might have evolved a mutualistic relationship with early eukaryotic cells. Over time, the reproductive cycle of the chloroplasts and mitochondria became completely tied together with the early eukaryotic cell and the chloroplast and mitochondria lost the ability to live outside the cell. Support for this theory comes from the fact that DNA is found in both organelles and is very similar to other prokaryotic cells. Summary:
