- unstructured population
- all individuals are subject to the same general ecological pressures.
rates of growth, reproduction, and mortality are roughly the same for all individuals.
EX: bacterial colony
- structured populations individuals can differ from one another in ways that make some individuals more susceptible to mortality or more likely to reproduce than others.
EX: insects, sea turtles, trees, and fish.
In these cases, mortality is often much higher for younger (and/or smaller) individuals.
Reproduction is often delayed until individuals are older (and/or larger).