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Lecture 20

# Lecture 20 - Bio 121 Lecture 20 Demography and Life History...

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Bio 121 Lecture 20 - Demography and Life History Strategies A. Introduction a. Demography – study of vital statistics that affect population growth a.i. Age specific birth rates a.ii. Age specific death rates a.iii. N = No + b – d + immigration - emmigration B. Survivorship – mirror image or mortality (primary way in which population dynamics is measured a. Age specific survivorship a.i. Lx = proportion of original cohort (group of individuals born at the same time) surviving to age x a.i.1. Humans a.i.1.a. Highest mortality rate = 1 years old a.i.1.b. Lowest mortality rate = 12 years old a.ii. Age class = Nx a.ii.1. 1000 at beginning, lx = 1000/1000 = 1 a.ii.2. 180 after 1 time period, lx = 180/1000 = 0.18 a.ii.3. 100 after next time period, lx = 100/1000 = 0.1 a.ii.4. 79 after next time period, lx = 79/1000 = 0.079 a.ii.5. 68 after next time period, lx = 68/1000 = 0.068 a.ii.6. 0 after next time period, lx = 0/1000 = 0 a.iii. Example: 10 percent of females survive each year a.iii.1. L1 = (0.1)^2 a.iii.2. L2 = (0.1)^2 a.iii.3. L3 = (0.1)^3 b. Different survivorship b.i. Different species live different lengths of time b.ii.

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