Population Growth Exponential growth: The total number of individuals increases as the number of reproducing females in the population increases. Shows a “J” shaped (exponential) curve Population (numbers of individuals) Exponential growth phase Growth accelerating. Lag phase Growth is slow due to small population size. Generations

Environmental Limits on Population Growth Logistic growth: 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 Carrying capacity (K) -The total number of individuals an environment can hold. Exponential growth phase Population (numbers of individuals) Lag phase Generations

r and k strategists r- strategist k- strategist Population (numbers of individuals) r- strategist k- strategist Generations

r and k strategists r-strategists k-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.