BIOL 220 Lecture Notes - Lecture 13: Harold Urey, Stanley Miller, Cambrian Explosion
Lecture 13
BIO 220
Early Metabolism
Early Metabolism
oAnaerobic oxidation-reduction reactions
Oxidized molecules were generated by reactions driven by UV light
oLight driven ion pumps
Such as bacteriorhodopsin of haloarchaea; could have conducted the first kind
of autotrophy
oMethanogenesis
Methanogenic archaea combine H2 and CO2 to produce CH4 and H2O
BIF
oAn extraordinary event in the planets history was the evolution of the first oxygenic
phototrophs:
Cyanobacteria that split water to form O2
oEvidence for O2 in the biosphere comes from oxidation states of minerals, particularly
those containing iron
The layers of iron oxide suggest periods of alternating oxygen-rich and anoxic
conditions
These layers are called banded iron formations
Or BIFs
oA common form of banded iron formations consists of gray layers of silicon dioxide
alternating with layers colored red by iron oxides and iron oxyhydroxides
oBanded iron formations are widespread around the world and provide our major
sources of iron ore
oThe Archaean and early Proterozoic eons experienced fluctuating O2 levels in the
atmosphere
These fluctuations could have led to oscillating levels of iron oxide, thus
producing bands in the sediment, as microbes used up all of the oxygen
oAlternatively, Dianne Newman, proposed that the iron oxides arose directly from
anaerobic photosynthesis
Important Dates
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Document Summary
Oxidized molecules were generated by reactions driven by uv light: light driven ion pumps. Such as bacteriorhodopsin of haloarchaea; could have conducted the first kind of autotrophy: methanogenesis. Methanogenic archaea combine h2 and co2 to produce ch4 and h2o. Bif: an extraordinary event in the planets history was the evolution of the first oxygenic phototrophs: Cyanobacteria that split water to form o2: evidence for o2 in the biosphere comes from oxidation states of minerals, particularly those containing iron. The layers of iron oxide suggest periods of alternating oxygen-rich and anoxic conditions. These fluctuations could have led to oscillating levels of iron oxide, thus producing bands in the sediment, as microbes used up all of the oxygen: alternatively, dianne newman, proposed that the iron oxides arose directly from anaerobic photosynthesis. Origin of earth: 3. 5 billion years ago. Oxygen accumulates due to photosynthesis: 2. 1 billion years ago. Eukaryotes first nucleated cells (single celled: 1. 2 billion years ago.
