BIOL 1F90 Lecture Notes - Lecture 2: Archean, Multicellular Organism, Archaea
12 Jan 2016
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Document Summary
Near end of ordovician, denovian, permian, triassic, cretaceous periods. Geologic time periods are often based on mass extinctions. Organisms buried quickly and heard plants replaced by minerals. Older rock is deeper and older organisms are deeper in the rock bed. Insects and seeds can also fossilize in amber (tree sap) Fossils can be dated using elemental isotopes in accompanying rock. Half-life - length of time required for exactly one half life of the original isotope to decay. Measure amount of a given isotope as well as the amount of isotope produced when isotope decays. Expect fossil record to underestimate actual date species came into existence. Anatomy - hard vs soft bodies - hard parts get fossilized and left behind, soft don t. Size - large vs small - large are more likely to be found, overrepresented in record. Number - abundant vs rare - more of the species means more likely one was fossilized.
