Population Ecology

Population

• All the organisms of a species that live in a an area at a certain time

• Populations change when –new members are added or –members leave or die

Birth

• The main way new members are added.• Birth Rate – number of births in a certain

amount of time–Example: births per year

Death

• Deaths are the main way members leave a population.

• Death rate = number of deaths in a certain amount of time Example: deaths per year

Immigration

• Organisms move in from another environment

• Causes a population to increase

Emigration

• Some organisms leave the environment to go somewhere else.

• Causes a population decrease

Population Change

Immigration

Births Deaths

Emigration

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Population Density

• Measurement of population per unit area or unit volumeExamples: Wolves per square km.

Bacteria per ml.

• If a population increases or decreases in a given area, population density also increases or decreases

Calculate Population Density

• If Yellowstone National Park has 400 wolves and covers an area of 9000 square km., what is the population density of wolves in Yellowstone?

• _450 wolves = 0.05 wolves/km² 9000 km²

Limiting Factors

• Any factor that limits the growth of a population in an ecosystem

• May be biotic or abiotic• Examples– Climate– Food– Water– Space– Shelter

Carrying Capacity

• The maximum number of organisms that can survive in a particular ecosystem.

• When a population reaches its carrying capacity, it cannot grow any larger