Download Logistics and Exponential Population Growth in the Ecology | BIOL 250 and more Study notes Ecology and Environment in PDF only on Docsity! 1 Today’s Outline Ecology (BIOL 250) Lecture 10: Population Growth Exponential & Logistic Growth Density Dependant & independent Limitations Offspring Number Versus Size Intrinsic rate of increase !Continuous population growth in an unlimited environment can be modeled exponentially. dN/dt = rmax N !As population size (N) increases, rate of population increase (dN/dt) gets larger. Exponential Population Growth Exponential Population Growth dN/dt = rmax N Logistic Population Growth Yeast Cells Logistic Population Growth !As resources are depleted, population growth rate slows and eventually stops: logistic population growth. "Sigmoid (S-shaped) population growth curve. "Carrying capacity (K) is the number of individuals of a population the environment can support. !Finite amount of resources can only support a finite number of individuals. Logistic Growth 2 Logistic Population Growth dN/dt = rmaxN(1-N/K) !rmax = Maximum per capita rate of increase under ideal conditions. !When N nears K, the right side of the equation nears zero. "As population size increases, logistic growth rate becomes a small fraction of growth rate. !Highest when N=K/2. !N/K = Environmental resistance. Logistic Population Growth What causes the rate r to change? Limits to Population Growth !Environment limits population growth by altering birth and death rates. "Density-dependent factors !Resource competition, Predation, Disease "Density-independent factors !Natural disasters Density Independent Factors -Galapagos Finch Population Growth- !Boag and Grant (1984) - Geospiza fortis was numerically dominant finch (1,200). !After drought of 1977, population fell to (180). !Food plants failed to produce seed crop. !Boag and Grant (1984) - Geospiza fortis was numerically dominant finch (1,200). !After drought of 1977, population fell to (180). !Food plants failed to produce seed crop. !1983 - 10x normal rainfall caused population to grow (1,100) due to abundance of seeds and caterpillars. Density Independent Factors -Galapagos Finch Population Growth- Density Independent Factors -Galapagos Finch Population Growth-
