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Unformatted text preview: BSCI 106 Outline 5 Fall 2008, p.1 Dr. Sara Via World Population Growth Density-dependent growth (continued) N follows a sigmoid shape-- asymptote at N = K N = r max (K-N) *N K N = r actual *N if (b-d) depends on density, then births and deaths should eventually balance pop. size stabilizes around N where b=d This N = carrying capacity, i.e., K Logistic Growth Applied Maximum sustainable yield (MSY) Fisheries The goal: Harvest the maximum number of individuals possible without reducing the population size over the long term The solution: Keep fish population at size where is N is greatest (make sure you can fill in the graphs and know how this works) A few warnings Estimating of K tricky K is usually variable Age structure matters Harvesting the large fish and replacing them with small will reduce r (why??) - What if one group takes too many fish? Etc, etc. Next complication! b and d change through lifetime!! BSCI 106 Outline 5 Fall 2008, p.2 Dr. Sara Via age-specific fecundity (birth rate) age-specific survival (death rate) Demography: how do age-specific b and d shape - Population growth - number of individuals in each age group - The effects are predictable!...
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- Fall '08