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 timeExample: 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

Immigration Births Deaths Emigration

Population Density Measurement of population per unit area or unit volume Examples: 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