Populations

Terms:
population, metapopulation, distribution, density, uniform, random, and clumped dispersion, demography, growth rate (r), intrinsic and realized growth rates, death rate (d), birth rate (b), emigration, immigration, exponential and logistic growth, density-dependent and density-independent factors, carrying capacity (K), Allee effect, source and sink areas

Allee effect:  The effect where populations at high or low densities begin to decline from negative growth rates. 

birth rate: The average number of births per individual per unit of time.

carrying capacity (K): The point where the realized growth of a population equals zero due to density-dependent factors that affect birth and death rates..

clumped dispersion: Refers to clumps of individuals of the same species scattered throughout the range of that species.

death rate: The average number of deaths per individual per unit of time.

demography: The study of vital statistics of a population, including birth and death rates, age of first breeding, and fecundity.

density: The number of individuals per area within the range of a species.

density-dependent factors:  Factors (e.g., disease, starvation, lack of nesting space) that cause declines in birth rates or increases in death rates due to intraspecific competition with increasing population density. 

density-independent factors:  Factors (e.g., fires, floods) that cause declines in birth rates or increases in death rates from events unrelated to population density. 

distribution: Total geographic range of all populations of a species, including gaps between populations.

emigration: The movement of individuals out of a population to a new area.

exponential growth: A population growth model where the rate of increase or decrease of a population is unaffected by intra and interspecific competition or other factors affecting growth.

growth rate (r): The mean rate of growth of a population at any given time calculated by birth minus death rates.

immigration: The movement of new individuals into a population from a different area.

intrinsic growth rate: The mean rate of growth of a population calculated by birth minus death rates when the population is free of competition with other species and from other factors that affect growth. 

logistic growth: A population growth model where the intrinsic rate of increase of a population slows or decreases to its realized growth rate when it is affected by intraspecific competition and density-dependent factors.

metapopulation: A population of populations, interconnected by immigration, emigration, and gene flow. 

population: A group of individuals of the same species that interact with each other in the same place at the same time.

random dispersion: Random spacing of individuals of the same species within an area.

realized growth rate: The mean rate of growth of a population at any given time calculated by birth minus death rates when the population is affected by inter and/or intraspecific competition and other factors that affect growth.

sink area: A region where a population is in continuous decline and must be supplemented through immigration to sustain itself..

source area: A region where a population is in continuous increase and individuals emigrate to new areas.

uniform dispersion: Even spacing of individuals of the same species within an area.