BIO 3115 Lecture Notes - Lecture 15: Hypothecated Tax, Black-Footed Ferret, Genetic Drift
19 Mar 2018
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Lecture 15 - extinction forces ii: stochastic forces. Random variation in population, unpredictable but can be modelled. Can be large compared to pop mean values. Some risks to be more susceptible to larger stochastic forces. Eg the dusky seaside sparrow had a small population, chance event, all the females died, 6 males survived. Effects of random events on the survival and/or reproduction of individuals cause demographic uncertainty. Can also have semelparous (reproduce once), if small pop can have reproductive failure, can have a biased sex ratio. In multiple reproductive events, usually can balance the sex ratio but sometimes no. Also in small pops, a biased sex ratio can be mucho no bueno. Unpredictable events like weather, food supply, population density of competitor, parasites, predators. Now many more extreme events eg 100 year floods every 5 years. Smaller populations and pops with small range are especially susceptible.
