GEL 107 Lecture Notes - Lecture 25: Background Extinction Rate, Global Cooling, Organism
Document Summary
Mass extinctions: sharp decline in diversity, global, effects majority of clades, faster. Background extinctions: natural turnover of taxa, effects a few habitats, affects a few clades, slower. Catastrophic mass extinction: abrupt, global event, synchronous extinctions at geological boundary, few if any survivors, origination after extinctions. Stepped mass extinction: species sensitive to change go extinct first, followed subsequently by increasingly more resistant species, elevated extinction rates across geological boundary. Graded mass extinction: typical background extinction rate leading up to geological boundary, high background extinction rate across geological boundary, typical background extinction rate passed geological boundary. South pole glaciation as gondwana moves southward. Upllft of appalachian mountains exposes rocks to weathering, leads to locking atmospheric carbon in rocks. O18/o16 in sample divided by o18o16 in standard. Morphological selectivity: different species sharing convergent, morphology go extinct, easy to identify pattern, hard to interpret.
