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Unformatted text preview: 11/14/10 1 Lecture 33: Extinction Predicting extinction Causes of population declines Causes of extinction Example: Dusky Seaside Sparrow Last Tasmanian Tigers in Captivity, 1933 Brown Tree Snake from the USDA Website Causes of Extinction Loss of ___________________ ________________ stochasticity ________________ stochasticity _____________________ Loss of genetic variation Caused by lack of _____________ & other problems in very small populations ( <50 individuals). Example: _____________ Demographic stochasticity* Random changes in characteristics of small populations ( _______ individuals). __________________________, breeding success, etc. *(stochasticity = randomness) 11/14/10 2 Environmental stochasticity Random changes in local environment affecting small populations ( ________ individuals) Examples: An unusually late frost or a very wet spring Catastrophes Larger, rare environmental events. Can affect populations of _________ ____________ . Examples: hurricanes, large forest fire, widespread disease outbreak, etc. Take-home rules If your population is very small (<500), then management should _______________________....
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- Fall '08