19.3 Earth's Early History

proteinoid microspheres
Under certain conditions, large organic molecules form tiny bubbles called…
Have some characters of living systems – have selective permeable membrane – simple means of storing and releasing energy
endosymbiotic theory
symbiotic relationship evolved over time, between primitive eukaryotic cells and the prokaryotic cells within them
1. one hypothesis proposed that mitochondria evolved from prokaryotes, which used oxygen to generate energy rich ATP
2. another hyp0thesis proposed chloroplast evolved from endosymbiotic prokaryote that had ability to photosynthesize
How old is earth?
4.6 billion years old
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What was the early atmosphere of earth made of?
Early Earth’s Atmosphere contained little or no oxygen and principally composed of carbon dioxide, water vapor and nitrogen, less amounts carbon monoxide, hydrogen sulfide, and hydrogen cyanide.
what was the color of earths early atmosphere?
During stanley mullers expirement, what kind of molecule was formed as an end product?
amino acids
Did RNA exist before DNA?
Could RNA replicate or form on its own?
Why did some life forms become extinct during the later years of early earth?
Rise of oxygen in the atmosphere
did some life forms evolve from the oxygen in the atmosphere?
Miller Urey Experiment
1. Water heated and water vapor forms
2. Mixture of methane, ammonia and hydrogen added to water vapor.
3. gases are bombarded by sparks of electricity
4. cold water condenses the gases causing droplets to form
5. after a week, liquid collected contains amino acids and other organic compounds
Evolution of RNA and DNA
Inorganic matter –> simple organic molecules –> RNA nucleotides –> RNA able to replicate, synthesize proteins, and helps DNA function in information storage and retrieval
Production of Free Oxygen
1. Microscopic fossils of prokaryotes resembling bacteria found in Archean rocks evolved in absence of oxygen 3.5 billion years ago
2. 2.2 billion years ago photosynthetic bacteria churned out oxygen which combines with iron in the oceans –> iron oxide, sank in the bottom of the ocean
3. oxygen accumulated in environment which drove early life forms to extinction and new life forms evolved with metabolic pathways using oxygen
modern evidence
lynn Margulis in 1960 noted that
1. Mitochondria and chloroplast contain DNA sismilar to bacterial DNA
2. mitochondria and chloroplast have ribosomes
3. They reproduce by binary fission when cells containing them divide by mitosis
Sexual Reproduction
sped up evolutionary change, and increases genetic variation

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