GEOL 107 Lecture Notes - Lecture 11: Crown Group, List Of Virtual Boy Games, Evolutionary Radiation
18 Oct 2016
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Last lecture before midterm and virtual lab test. Most profound and rapid diversification event (evolutionary radiation) in the history of life. Exponential rise in diversity throughout the early cambrian. Reflects the emergence of skeletons and brains. No evidence of thought or patterned behaviour, just individual responses by individual organisms to individual stimuli: cambrian burrows show consistent, complex patterns that are repeated worldwide. Three main innovations: complex patterns of deposit-feeding and predation, vertical dwelling burrows, systematic meandering burrows. Trace fossils define the position of the ediacaran-cambrian boundary. Middle cambrian (505 ma) shale near field, b. c. Exceptional preservation of hard and soft-bodied marine animals. One of the most important fossil lagerstatten of all time. Causes of the cambrian explosion: rise in oxygen (threshold factor, cambrian explosion is the latter part of the ediacaran oxygenation event, formation of collagen required >10% present atmospheric levels by the. Ediacaran: exoskeleton requires even oxygen levels, higher oxygenation especially favours predators, a key part of the.
