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Population Growth •Exponential growth: Population (numbers of individuals) –The total number of individuals increases as the number of reproducing females in the population increases. –Shows a “J” shaped (exponential) curve Lag phase Growth is slow due to small population size. Generations Exponential growth phase Growth accelerating. Environmental Limits on Population Growth •Logistic growth: Population (numbers of individuals) –Populations are dependent upon finite resources for survival. –This will limit the exponential growth phase of a population curve –Shows an “S” shaped (sigmoidal) curve Equilibrium phase Deceleration phase Exponential growth phase Lag phase Generations Carrying capacity (K) -The total number of individuals an environment can hold. Population (numbers of individuals) r and k strategists r- strategist Generations k- strategist r and k strategists r-strategists • • • • • • • Populations never move from the “r” phase of the growth curve. Produce far more offspring than will survive Population never reaches “reproductive potential.” Give no care to offspring Population is controlled by density independent factors (i.e. climatic events, fire, etc.) Resources are stable and plentiful. i.e. bacteria, fungi, insects, small rodents. k-strategists •Populations exist at or near the “k” phase of the growth curve. •Expand tremendous energy raising few offspring. •Give a lot of care to offspring •Population is near “reproductive capacity.” •Population is controlled by density dependent factors (i.e. competition predation, etc.) •There is a high degree of competition for limited resources. •i.e. long lived plants, large mammals, humans, raptors.