Population Density Number of individuals per unit of area.
Immigration Movement of individuals into an area occupied by an existing population.
Emigration Movement of individuals out of an area.
Exponential Growth Growth pattern in which the individuals in a population reproduce at a constant rate.
Logistic Growth Growth pattern in which a population’s growth rate slows or stops following a period of exponential growth.
Carrying Capacity Largest number of individuals of a population that a given environment can support.
Key Concept What characteristics are used to describe a population? Three important characteristics of a population are its geographic distribution, density, and growth rate.
Key Concept What factors affect population size? Three factors can affect population size: the number of births, the number of deaths, and the number of individuals that enter or leave the population.
Key Concept What are exponential growth and logistic growth? Under ideal conditions with unlimited resources, a population will grow exponentially and as resources become less available, the growth of a population slows or stops.