
Life tables describe how
survival and reproductive rates vary with age, body size, or life cycle stage

N_{x} =
Number of individuals alive at age x.

S_{x} =
Survival rate; (Nx+1/Nx); proportion of individuals of age x that survive to age x + 1

l_{x} =
Survivorship; Nx/N0; proportion of individuals that survive from birth (age 0) to age x

F_{x} =
Fecundity; average number of offspring born to a female while she is of age x

Static Life Table
 Provides a snapshot of all cohorts at one time
 Provides data on: Survivorship (lx) Fecundity (Fx)
 No Survival Rate (Sx)

Survivorship curves
A plot of the number of individuals from a cohort (actual or estimated) that will survive to reach different ages.

Three types of survivorship curves
 Type I: Most individuals survive until old age
 Type II: Constant chance of dying
 Type III: Most individuals die young

Age structure:
The proportions of the population in each age class (e.g., 20/100, 30/100, 50/100)

Age class:
All individuals within a population that fall in a range of ages (e.g., 01, 12, 23).

Age structure can influence
how rapidly populations grow

 and  do not change in life tables
fixed agespecific survivorship and fecundity

When lambda is below one, population is
decreasing. When above one, increasing

Understanding population growth requires knowing when  and  occur
births and deaths occur.

Life tables describe how survival and reproductive rates vary with (3)
age, body size, or life cycle stage

Fixed agespecific survival and fecundity produce (2)
unchanging population growth or decline (λ) and a stable age distribution

Changing agespecific survival and fecundity alters and 
population growth and stable age distributions

λ can stand for
 1)the proportional change in population size between generations
 2)the geometric population growth rate (finite rate of increase)

Geometric population growth:
 Reproduction occurs at discrete intervals.
 Example: Organisms that breed once a year.

λ formula
(N_{t } +1)/N_{t}

dN/dt =
rate of change in the population at each instant of time

(dN/dt)=rN what does each part stand for?
 dN/dt = rate of change in the population at each instant of time
 r = The intrinsic rate of natural increase; indicates how rapidly the population is growing
 N = the current population size

Populations growing exponentially are represented with a 
continuous line

t_{d }
doubling time, of a population is the number of years it will take the population to double in size


