# Ecology Chapter 9 ECU

 Life tables describe how survival and reproductive rates vary with age, body size, or life cycle stage Nx = Number of individuals alive at age x. Sx = Survival rate; (Nx+1/Nx); proportion of individuals of age x that survive to age x + 1 lx = Survivorship; Nx/N0; proportion of individuals that survive from birth (age 0) to age x Fx = 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 timeProvides 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 ageType II: Constant chance of dyingType 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., 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 generations2)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 (Nt +1)/Nt 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 timer = The intrinsic rate of natural increase; indicates how rapidly the population is growingN = the current population size Populations growing exponentially are represented with a ------------ continuous line td  doubling time, of a population is the number of years it will take the population to double in size doubling time formula Authorzzto ID173241 Card SetEcology Chapter 9 ECU DescriptionEcology Chapter 9 ECU Updated2012-09-27T13:19:41Z Show Answers