POPULATION ECOLOGY V
DEMOGRAPHIC TECHNIQUES
I. Life tables: age specific population parameters
A. Types of Life Table
1. Cohort life tables - a group of equal-aged individuals is followed through time
2. Static (Stationary, Time specific, Current or Vertical) - based on a cross section of
the whole population at a point in time
a. Age of death observed
b. Age structure directly observed
3. Life table terms
a. x = age of the age group
b. lx = survivorship of individuals aged x
c. dx = number dying in interval x to x+1
d. qx = death rate for individuals aged x
qx = dx / lx
e. ex = expectation of future life of individuals aged x
where ex = Tx/lx and Tx = ∑ Lx and Lx = lx+lx+1/2
II. Survivorship curves - lx vs age
A. "types" of survivorship curve
1. Low mortality in early life
2. Constant probability of death at all ages
3. High mortality of young age classes
III. Mortality curves qx vs age
(same as above)
IV. Age specific fecundity - mx
The average number of offspring from females aged x
NOTE R0 = ∑ lxmx
The net reproductive rate is the sum of the product of age specific survivorship and fecundity
Va the reproductive value of an individual aged a:
Va = era/la ∫ e-rx lxmx
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