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15 Cards in this Set
- Front
- Back
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Stages of Earth's atmosphere |
1. Jupiter - rich in H and He from solar nebula, burned off by solar wind 2. Venus - mostly carbon dioxide due to volcanic activity 3. Rich in oxygen - from anaerobic synthesis of first forms of life |
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Basic stages of development |
Raw ingredients -> monomers -> polymers -> cell membrane -> reproduction -> living cell |
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Examples of monomers |
water, methane, ammonia, hydrogen and energy - all you needed to do was add energy to the raw ingredients |
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Examples of raw ingredients |
carbon dioxide, water, carbon monoxide, nitrogen gasses, sulfur gasses |
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How did polymers form? |
assumed through concentration and dehydration of monomers through evaporation in i.e. hot springs or, perhaps from mineral templates |
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Origin of the cell membrane |
lipids can spontaneously form liposomes (hollow bubbles) Proteins may also form microspheres when dehydrated and agitated |
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Important properties of the cell wall |
maintain seperate phases in water maintain electric, pH and redox gradients in membrane |
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Significance of RNA to reproduction |
RNA can act as information that can be replicated but can also function like an enzyme - therefore RNA came first because it could read and replicate itself |
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Naked Gene Hypothesis |
RNA came before anything and was floating around alone |
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Rationale of the Naked Gene Hypothesis |
Earliest form of life was energy- harvesting RNA that could replicate itself RNA molecules most efficient at energy harvesting and protecting themselves from environmental changes would be selected for Natural selection would build complex metabolic and regulation systems incorporating protein enzymes RNA that could replicate in double-stranded form would be successful in having two copies of the code, allowing better detection for error |
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Problems with naked gene hypothesis |
RNA and DNA are very complex - need a high concentration of building blocks to polymerize them |
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Replication of RNA in 2 Steps |
Single strand of RNA present, each link attracts a complimentary out of prebiotic soup Could be separated using new "mirror image" to duplicate itself |
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Sydney Fox - Replication beginning from proteins |
Sheltered lagoons with tiny proteinoid microspheres which catalyze chemical reactions and form outer surfaces acting like cell membranes, DNA/RNA formed on proteinoid enzyme templates, then evolve to function as replicator molecules |
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Clay Critter Hypothesis |
Believes that the template for life was a charged mineral that attracted the necessary monomers to form polymers to a surface and that's how the assembled originally Kept adding layers to the mineral (that's how they normally grow) until it was not needed any more DNA and RNA ultimately replace clay-based "genes" |
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Panspermia Hypothesis |
Life on earth originated elsewhere |
