BIO 200 Lecture 15: Lecture Guide
28 Nov 2017
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Document Summary
A brief tour through the history of time (on earth) Rotating disk of dense gas and dust surrounding a young newly formed star. Pressure within the central mass of the protoplanetary disk triggered nuclear fusion - heat due to concentration of mass in the center. Large body of matter in orbit around the sun or a star and thought to be developing into a planet - perturbations in the outer rings of the disk. Life was confined to oceans and organisms were small - lived in shallow seas - began to team with microscopic prokaryotes. Proterozoic - first eukaryotes and small multicellular animals fed on microorganisms. Plankton were strained from the water and eaten by slightly larger filter- feeding animals. Others ingested sediments on the seafloor and digested remains of organisms. Limited diversity of multicellular eukaryotes - increased oxygen levels - series of intensely cold periods resulting in ice covered seas and glacier covered continents.
