BIO 200 Lecture Notes - Lecture 2: Precambrian, Paleozoic, Protoplanetary Disk
19 Sep 2016
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Document Summary
Time scales: the formation of the earth, what happens next: four eras, a brief tour through the history of time (on earth) Origin of life: extraterrestrial origins, what is life, the earth before life originated, four steps. Large rotating cloud of dust, rocks, and gas. Composed of hydrogen and helium in the big bang. Destroyed 4. 6 bya when a star nearby experienced a supernova and shockwave blew away the cloud: formation of our sun. Most of mass in disk concentrated in the center and began to heat up. Enormous amount of heat nuclear fusion of hydrogen to helium sun: protoplanet. Small perturbations (deviations from the system) caused by collisions of matter remained in the disk formed protoplanets. Gravity caused matter to condense around protoplanets. Protoplanet that became earth was completed in 10-20 million years: precambrian supereon. Was consisted of hadean, archean, and proterozoic eons. Life during this time consisted of unicellular organisms.
