Populations

Populations are the structural and function unit that is larger than an individual.  They include all individuals of a species in a given area that can interbreed.

Characteristics of populations that are of interest to ecologists:

- number of individuals

- population density (or how many individuals are found in a given area) 

- spatial distribution: a) uniform (situation of high competition or territoriality) b) random (low population, constant environment - very rare in nature) c) clumped (determined by environmental factors or reproductive behaviours)

- age distribution

Age distribution graph

- gender distribution (also shown in graph above)

- dynamics: a) migration (moving to or from a location) b) birth/death rates c) reproductive potential (maximum possible offspring if there are no internal or external limits) vs. actual reproductive output 

-population growth patterns: a) exponential growth occurs when a small population has a large number of offspring.  In nature this kind of growth only occurs under special conditions and only for a short while

Exponential growth

The environment's carrying capacity limits population growth, resulting in restricted growth, when the number of individuals in the population stabilizes based on the environmental factors.  This is also called b) logistic growth

Logistic growth

The population will not be set at an exact number, but will oscillate near the carrying capacity.