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)BirthsEmigration (leaving)Deaths

Population Density

Population Density:The number of individuals that live in

a defined areaHelps scientists determine how

crowded an area is

Formula:# of individualsArea

(units2)

= 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 resourcesNo more will fit!!!

Population Growth

Carrying CapacityThe 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 & diseaseHave 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