Population Ecology

Levels of Ecological Organization

HABITAT – Where organism lives NICHE – An organism’s role in a community and the resources that it uses Specialist – Species with a narrow niche….have very specific requirements Example: Panda Generalist – Species with a broad niche – able to use wide variety of habitats and resources

Population Characteristics SIZE – Number of organisms present at a given time Extinctions often preceded by DECLINE in population size

Population Density Number of individuals within a population per unit area

Population Distribution Spatial arrangement of organisms within an area

Populations may grow, shrink, or remain stable Births within the population (natality) Deaths within the population (mortality) Immigration – arrival of individuals from outside the population Emigration – departure of individuals from the population

Growth Rate of Population Express birth and death rates per 1,000 individuals for a given time period. Referred to as “Crude” birth rate or death rate Growth Rate = (Crude birth rate + immigration rate) – (Crude death rate + emigration rate) Example: (18/1000 + 5/1000) – (10/1000 + 7/1000) = 6/1000 This population of 1000 in one year will reach 1006 in next year. Growth Rate is expressed as percentage: Growth rate x 100% 6/1000 x 100% = 0.6%

Exponential Growth Unregulated populations increase by exponential growth (fixed percentage each year) J shaped growth curve Occurs when organisms introduced to “new” environment Examples: Mold growing on piece of bread, Bacteria colonizing recently dead animal, Scots Pine tree after retreat of glaciers

Logistic Growth Limiting factors restrain population growth S shaped growth curve

Limiting Factors Density Dependent – Limiting factors that have stronger effect on large, dense populations than small, less crowded populations Ex: Disease, Predation, Competition for resources food, water, space Density Independent - Same effect regardless of population size Ex: Natural disasters floods, fires, hurricanes, etc. and extremes in temperature Carrying Capacity – Maximum population size of a species that a given environment can support

Biotic Potential and Reproductive Strategies

Survivorship Curves

Conservation of Biodiversity Creating Protected Areas for endangered species – National Parks and Reserves Ecotourism