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11 Cards in this Set
- Front
- Back
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Possibilities of how the first cell came about |
Essential ingredients for life were assembled in an aquatic environment and were later incorporated into cell membrane Cell membrane itself acted to bring ingredients together, and eventually incorporated inside membrane Complex ingredients assembled on charged mineral surfaces, and later encapsulated in a cell membrane (perhaps an organic film on the surface of the mineral) |
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U-Bearing conglomerates suggest what in the atmosphere of early earth |
Absence of oxygen because uranium is insoluble in absence of oxygen |
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Significance of iron in land sediment |
Soils begin iron deficient - all the iron was dissolved in water and not precipitated onto land Soils then begin to see iron which indicates enough oxygen in the atmosphere to begin to precipitate iron on land before it reaches the river sediment |
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Earliest fossils |
Single-celled prokaryote fossils from Archean eon Stromatolites Most likely cyanobacteria |
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BIF deposition |
Seen in Proterozoic Indicates enough oxygen to form iron oxides in sea but not enough to rust iron on land (is soluble in absence of oxygen) Alternating pale bands are chert - nothing using silica to make its shells so we see lots of chert deposited |
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First definite appearance of redbeds |
Proterozoic - land-derived sediments containing iron oxides Indicate enough free oxygen in atmosphere to oxidize iron in river water before it reached the sea |
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Significance of stromatolites |
Made of cyanobacteria with photosynthesize
The sediment covering protected them from harsh radiation of early earth (due to lack of ozone) - nothing could live in sun Photosynthesis also indicates to presence of light |
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Before 2.5 billion years ago (regarding atmosphere/hydrosphere) |
there was almost no oxygen |
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From 2.5 to 2.0 billion years ago (regarding BIF) |
enough oxygen in sea water to form magentite and hematite in BIF |
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Beginning around 2.0 billion years ago (redbeds) |
enough oxygen to oxidize iron on land and cause it to rust |
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Evolution of prokaryotes was extremely.... |
slow |
