Ch12 Temporal and Spatial Dynamics of Populations.docx

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Spencer Barrett

chapter 12: TEMPORAL AND SPATIAL DYNAMICS OF POPULATIONS 1. pop. fluctuate in response to:  envmtal variations  unstable intrinsic properties  pop. of species w/ larger bodies and longer life spans respond less rapidly to changes in their envmts  the age structure of a pop. often indicates variations in recruitment over time  ex. seedlings of a certain tree species tend to become established in forests primarily following a major disturbance 2. discrete-time models of density-dependant populations:  show pop. sizes tend to oscillate when disturbed  behaviour depends on the proportional rate of increase (R) per unit of time  0 < R < 1 : pop. size approach equilibrium (K) w/o oscillation  1 < R < 2 : pop. size undergoes damped oscillations and eventually settles down to K  R > 2 : pop. size oscillates in increasing amplitude (limit cycles) until –  a stable limit cycle is achieved or;  the pop fluctuates irregularly (chaos) 3. continuous-time models of density-dependant pop.:  predict pop. cycles when there are time delays  behaviour depends on the product of the intrinsic rate of increase (r) and the time delay (τ)  0 < rτ < 1/e (0.37) : no oscillation  rτ < π/2 (1.6) : damped oscillations  π/2 > rτ : limit cycles w/ amplitude > 4τ
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