ECOLOGISTS STUDY ENVIRONMENTS AT DIFFERENT LEVELS OF ORGANIZATION. Population Ecology Organism  Population  Community  Ecosystem  Biome

Population Ecology Population:  all the organisms that both belong to the same group or species and live in the same geographical area  Specific species at the same place at the same time Example:  1,738 trout in Kentucky Lake in 1986

Population Size The size of a population is always changing! Four factors affect the size of a population:  Immigration (coming in)  Births  Emigration (leaving)  Deaths

Population Density Population Density:  The number of individuals that live in a defined area  Helps scientists determine how crowded an area is  Formula: # of individuals Area (units 2 ) = population density

Population Growth Population growth is based on available resources. FOOD WATER SHELTER

Population Growth Exponential Growth (J curve)  Rapid population increase due to an abundance of resources.

Population Growth Logistic Growth (s curve)  Due to a population facing limited resources No more will fit!!!

Population Growth Carrying Capacity  The maximum number of individuals that the environment can support  When resources run out the population cannot keep growing

Population Growth Ecological Factors limit population growth. Limiting Factors:  Something that keeps the size of a population down

Limiting Factors Density-dependent limiting factors:  Depend on the number of individuals in a given area.  Examples:  Predation  Competition (competing for resources)  Parasitism & disease  Have a larger effect in densely populated areas

Limiting Factors Density-independent limiting factors:  Limit a population’s growth regardless of the number of individuals  Examples:  Unusual weather  Natural disasters  Human activities