Unformatted text preview: Lecture #23 Date _______ Chapter 52 ~ Population Ecology Population characteristics Density~ # of individuals per unit of area counts sample size estimate indirect indicators mark-recapture Dispersion~ pattern of spacing random~ unpredictable, patternless
spacing (a) clumped~ patchy aggregation (b) uniform~ even spacing (c) Demography: factors that affect growth & decline of populations Birthrate (natality, fecundity)~ # of offspring produced Death rate (mortality) Age structure~ relative number of individuals of each age Survivorship curve~ plot of numbers still alive at each age Population Growth Models Exponential model (red) idealized population in an unlimited environment (Jcurve); r-selected species
(r=per capita growth rate) Logistic model (blue)
carrying capacity (K):
maximum population size that a particular environment can support (S-curve); K-selected species Population life history "strategies" r-selected (opportunistic) K-selected (equilibrial) Short maturation & lifespan Many (small) offspring; usually 1 (early) reproduction; no parental care High death rate Long maturation & lifespan Few (large) offspring; usually several (late) reproductions; extensive parental care Low death rate Population limiting factors Density-dependent factors
competition predation stress/crowding waste accumulation Density-independent factors
weather/climate periodic disturbances ...
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