Ch 25 notes - Chapter 25 Additional notes Evidence Chemical...

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Chapter 25: Additional notes Evidence Chemical and physical processes on early Earth, aided by the forces of natural selection, may have produced very simple cells through a sequence of four main stages 1. The abiotic (non-living) synthesis of small organic molecules, such as amino acids and nucleotides 2. The joining of these small molecules into macromolecules, including proteins and amino acids 3. The packaging of these molecules into “protobionts,” droplets with membranes that maintained an internal chemistry different from that of their surroundings 4. The origin of self-replicating molecules that eventually made inheritance possible Key events in Earth’s history Archean (origin of the earth) Proterozoic Palezoic (colonization of land) Mesozoic Cenozoic (humans) Synthesis of organic compounds on early earth The first atmosphere: made up primarily of methane and ammonia; neither were reducing or oxidizing Protobionts Two key properties of life: accurate replication and metabolism; neither can exist without the other Protobionts: collections of abiotically produced molecules surrounded by a
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