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Published byShanna Walters Modified over 9 years ago
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KEY CONCEPT The origin of life on Earth remains a puzzle.
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NGSSS SC.912.L.15.8 Describe the scientific explanations of the origin of life on Earth. (MODERATE)
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Earth was very different billions of years ago.
There have been many hypotheses of Earth’s origins. The most widely accepted hypothesis of Earth’s origins is the nebula hypothesis.
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Several sets of hypotheses propose how life began on Earth.
There are two organic molecule hypotheses. 1.Miller-Urey experiment- Demonstrated that organic compounds could be made by passing a electric current (simulating lightning) through a closed system that held a mixture of gasses and water. electrodes heat source amino acids water “atmosphere” “ocean” Gasses thought to be on early earth: ammonia, methane, hydrogen, Carbon dioxide. No oxygen
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There are two organic molecule hypotheses.
2. meteorite hypothesis- Amino acids may have arrived on Earth through meteorites or asteroid impact.
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There are different hypotheses of early cell structure.
iron-sulfide bubbles hypothesis- Biological molecule combined in in compartments of hydrothermal vents where organic molecules were concentrated - the walls of the compartment formed the cell membranes.
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There are different hypotheses of early cell structure.
lipid membrane hypothesis- lipid spheres could form around a variety of organic molecules.
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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.
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