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) = 6/1000This 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 sizeEx: 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