POPULATION DENSITY, DISTRIBUTION & GROWTH

 Density is a measure of how closely packed organisms are in a population  Calculated by … DENSITY # of individuals area (units 2 ) = population density

 Distribution refers to how organisms are spaced out in their habitat DISTRIBUTION

 A population’s size changes are the result of 4 factors  Births, deaths, immigration, emigration  Births and immigration increase size  Deaths and emigration decrease size GROWTH

 Population growth is first influenced by available resources  Food, water, territory  Populations grow exponentially if resources are unlimited GROWTH

 Resource limitations eventually slow a population’s growth  Logistic growth has a “leveling off” period of time  Population reaches its carrying capacity  Carrying capacity = maximum # of individuals habitat can support GROWTH

 Limits to growth fall into two categories  Density dependent limiting factors  Increase their pressure as population size grows  Examples: predation, competition, disease  Density independent limiting factors  Pressure remains constant regardless of population size  Examples: weather, natural disasters, seasonal changes LIMITS TO GROWTH