BISC 102 Study Guide - Final Guide: Banded Iron Formation, Petrified Wood, Hematite
19 Jan 2018
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Lec 6: early earth: earth = ~ 4. 6 by old. Constant meteorites bombarding (leads to evaporation of oceans) Atmosphere: h2o, n2, ch4, co2 atm lacked molecular oxygen (o2) H2o + co2 + light ---> ch2o + o2 (first photosynthetic pathways likely reduced other molecules: evidence of life. Sedimentary rock structures built by accumulation of sediment of photosynthetic cyanobacteria. The cyanobacteria have sticky surfaces ---> trap sediment. Iron oxides (especially hematite) provide evidence of oxygen. Banded iron formation: hydrothermal vents spew fe in water. Process: sedimentary rock compress + protect organisms from decomposers. Organic material compressed in carbon film (ex. leaf) Casts (ex. bark) + molds can form from imprints of original. Permineralization: original decomposes slowly and organic material replaced by minerals (ex. petrified wood) Prokaryotes that likely lived in deep sea hydrothermal vents. Earliest (what are believed to be) eukaryote fossils: 2. 1 bya: prokaryotes vs eukaryotes. Hypothesis: infolding of cell membrane = gave rise to nuclear membrane, endoplasmic reticulum.
