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Week 11, Lecture 3, Populations

# Week 11, Lecture 3, Populations - Population ecology Births...

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1 Lajoie – Populations ‘09 Population ecology Increase = Births - Deaths Births + Immigration = in pop size Death + Emigration = in pop size Most models assume no migration. http://www.census.gov/ipc/www/popclockworld.html Lajoie – Populations ‘09 b = birth rate per individual d = death rate per individual N = number of individuals 1) Exponential model I = (b - d) N Lajoie – Populations ‘09 Let (b - d) = r r = reproductive rate per individual Then if (b-d) > 0 then r is + ve popualtion if (b-d) < 0 then r is - ve population 1) Exponential model I = (b - d) N I = (b - d) N Lajoie – Populations ‘09 e.g. Population size = 90 individuals births = 25 deaths = 3 Birth rate b = 25/90 = 0.28 (per individual) Death rate d = 3/90 = 0.03 (per individual) 1) Exponential model r = (b - d) = (0.28 - 0.03) = 0.25 per capita increase I = r N = 0.25 x 90 = 23 new individuals for that generation Lajoie – Populations ‘09 90 + 25 – 3 = 112 22 new individuals 1) Exponential model A population has 1134 individuals with 114 births and 43 deaths b = / d = / = = r = (b-d) = = Population 1 r = Population 2 r = Lajoie – Populations ‘09

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