BIOL 1001 Lecture Notes - Lecture 6: Siberian Traps, Genetic Drift, Paleontology
14 Jan 2017
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Document Summary
Mass extinctions is the rapid extinction of large number of lineages scattered throughout the tree of life. Occurs when at least 60% of species present are wiped out within one million years. They are catastrophic episodes that wipe out huge numbers of species & lineages in a short ti(cid:373)e. the(cid:455)"re opposite if adaptive radiatio(cid:374)s. Background extinctions revers to the lower, average rate of extinction observed when mass extinctions is not occurring. Background extinctions: occur when normal environmental change, emerging diseases or competitions within other species reduce certain populations to zero. Mass extinctions result from extraordinary, sudden & temporary changed in the environment. Pecies do(cid:374)"t die out because individuals are poorly adapted to normal or gradually changing environmental conditions. Species die out from exposure to harsh, short-term conditions- such has huge volcanic eruptions or catastrophic sea level changes. Extinction depend on fitness of individuals under normal conditions. Largest flood basalts (molten rock that flows across earth) called siberian traps occurred.
