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4.5 to 3.8 Gyr ago, meteor bombardment may have killed off incipient life more than once before living microbes finally became establihed
Hadean eon
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3.8-2.5 Gyr ago, the earliest evidence of life, meteor bombardment was less frequence
Archaean eon
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Early metabolism: oxidation by UV light
anaerobic red-ox reactions
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Early metabolism: producing CH4 and H2O from H2 and CO2
methanogenesis
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Geological evidence for early life:
limestone sediment
stromatolites
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Models for the first cells:
small organic molecules arise abiotically from simple reduced chemical parked by lightning, which produced complex macromolecules that acquired the apparatus for self-replication and membrane compartmentalization
prebiotic soup
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Models for the first cells:
self-sustaining abiotic chemical reaction could have formed the basis of cellular metabolism
metabolist models
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Models for the first cells:
information molecule and catalysis (ribozyme)
RNA world
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Branching groups of related organisms
clades
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a group of species that share a common ancestor
monophyletic group
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The full description of branching divergence of a species is called...
phylogeny
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Name three fundamental mechanisms of evolution
- 1. random mutations
- 2. natural selection and adaptation
- 3. reductive (degenerative) evolution
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Temporal information contained in a macromolecular sequence, based on the acquisition of new random mutations in each round of DNA replication.
molecular clock
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Carl Woese used SSU rRNA phylogeny to reveal the existence of...
a third kind of life: archaea (in addition to two other domain - Bacteria and Eukarya)
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Encode products essential for transcription and translation
- interact with many cellular components
- tend to be transferred vertically
informational genes
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Encode product that govern metabolism, stress response, and pathogenicity
- function with relative independence
- more likely to be transferred horizontally
operational genes
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