Population Ecology

Population Dynamics Population Density: number of organisms per area. Dispersion: the pattern of spacing of a population within an area

Dispersion: the pattern of spacing of a population within an area Uniform dispersion: black bears Clumped: bison Random: deer

Limiting Factors: Factors that keep a population from continuing to increase in numbers indefinitely. Density independent factors Density dependent factors

Density Independent Factors: Any factor in the environment that doesn’t depend on the number of members of a population per unit area. Usually abiotic or part of natural phenomena, such as weather events Drought, extreme temperatures, tornados, hurricanes

Density Dependent Factors Any factor in the environment that depends on the number of members in a population per unit area. Biotic Factors: Disease, Competition, Parasites

Studying Dispersion and Population Density Quadrat Sampling: using a known small area to count the number of organisms within that area. This count is then used to generate data for a larger area. Random Sampling: Line Transect Sampling: Mark and Recapture:

http://www.isleroyalewolf.org/data/data/womoabund.html

Growth Rates Population Growth Rate: how fast a population grows. Takes into account the natality (birth) and mortality (death) rates. Emigrations: the number of organisms moving away from a population Immigration: the number of organisms moving into a population Usually emigration=immigration

Exponential Growth Model Population grows exponentially and passes its carrying capacity until some limiting factor slows the growth.

Logistic Growth Model Occurs when the population’s growth slows or stops following exponential growth, at the population’s carrying capacity.

Reproductive Patterns: R/K Selection Theory r-Strategists: rate strategy: orgainisms that live in environments with fluctuations in biotic and abiotic factors occur. Generally small organisms, short life spans and produce many offspring. Usually controlled by density independent factors and do not maintain carrying capacity Bacteria, insects and weeds Follow exponential growth models

K- strategists: carry capacity strategy: organisms that live in a predictable environment that does not change greatly from year to year. Generally larger orgainisms, long lifespans, few offspring, reaches equillibrium at carrying capacity. Great amounts of parental care Humans, elephants Follow logistic growth models

Human Population Growth Demography: the study of human population size, density, distribution, movement, and birth and death rates.

Human Population Growth: Why is the population growth decreasing???

Zero Population Growth: the birth plus immigtation equals the death plus emigration. Births and deaths occur at the same rate. The age structure of the population becomes equal.

Age Structure The number of males and females in each of three age groups: pre-reproductive (under 20), reproductive (20-44), and post reproductive (above 44)