Ecology Chapter 9 ECU
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Life tables describe how
survival and reproductive rates vary with age, body size, or life cycle stage
Number of individuals alive at age x.
Survival rate; (Nx+1/Nx); proportion of individuals of age x that survive to age x + 1
Survivorship; Nx/N0; proportion of individuals that survive from birth (age 0) to age 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)
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
The proportions of the population in each age class (e.g., 20/100, 30/100, 50/100)
All individuals within a population that fall in a range of ages (e.g., 0-1, 1-2, 2-3).
Age structure can influence
how rapidly populations grow
------ and ------ do not change in life tables
fixed age-specific 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 age-specific survival and fecundity produce (2)
unchanging population growth or decline (λ) and a stable age distribution
Changing age-specific 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.
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 ------------
doubling time, of a population is the number of years it will take the population to double in size
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