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Age Specific Fecundity Calculation Table
The two most basic parameters of a population are an individual?s likelihood of . Both of these parameters depend on the individual?s age, in most species (very young ones and very old ones do not breed and very young individuals often have high odds of mortality). These basic parameters are combined in a breeding, as life-tableand age-specific survivorship . From these two parameters, we can derive demographic information that allows measurement of the age-specific fecundityrate of population growth and projection of future population sizes.
Age is a variable, but it is generally broken into discrete continuous in demographic analysis, each potentially including a bout of reproduction. age-classes A set of individuals (a cohort) are observed through time, from birth to death, recording how many are still alive in each age class (at beginning of class usually, but can also be at mid-point of age class). E.g. Start with 500 newborns.
Survivorship from birth to age-class x/N(N for number)0 This is the likelihood of living to a given age. Age-specific survival is denoted sx. (s for survival)sx = Nx+1/N(x = lx+1/lx) lx decreases continually through age classes.
1/2 .number of offspring born to parent of age xFor each offspring produced, male and female parent each credited with offspring produced.
mx. Total lifetime reproduction in the absence of mortality. This is the average lifetime reproduction of an individual that lives to senescence, useful in considering potential population growth if all ecological limits (predation, competitors, disease, starvation) were removed for a population. GRR is rarely if ever attained in nature, but useful to consider how far below this a population is held by ecological limits.
lxmx. Average number of offspring produced by an individual in its lifetime, taking normal mortality into account. lx is the odds of living to age x, mx is the average # of kids produced at that age, so the product lxmx is the average number of kids produced by individuals of age x. Summed across all ages, this is average lifetime reproduction.
R0 < 1 individuals not fully replacing themselves, population shrinkingR0 = 1 individual exactly replacing themselves, population size stableR0 > 1 individuals more than replacing themselves, population growingThe schedule of reproduction ( mx curve) can be used to determine the .generation time, TT = Σ Where, The denominator (Σ Relationship of net reproductive rate (
r = ln when The equation This is solved by iteration 1. Use the approximate solution to get a close estimate of 2. Make an The true intrinsic rate of increase is r = 0.78, compared with original estimate of r = 0.72. |