BILD 3 Lecture Notes - Lecture 10: Radiometric Dating, Mesozoic, Paleozoic
Document Summary
History of life on earth: radiometric dating, changes in the fossil record. Fossil: any trace of organisms that lived in the past. Living fossil : no morphological change over very long time periods; no close living relatives. Isotopes: varieties of an element with different mass due to different numbers of neutrons in the nucleus: e. g. 14 c is used for more recent objects (carbon-14 dating: living organisms have a stable ratio of 14c/12c until they die, at which point 14 c decays predictably. In addition, fossils sandwiched in layers of sedimentary rock record a longitudinal slice of time. Changes in the fossil record: geological time scale, developed before darwin, based on distinctive fossil taxa, originally based on relative ages of fossils (younger rocks lie on top of older ones, some boundaries are mass extinctions. Three evolutionary milestones during precambrian: o 2 increase, eukaryotes appear, multicellularity arises.
