1. POPULATION DENSITY, DISTRIBUTION & GROWTH

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

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

4.  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

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

6.  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

7.  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