A population consists of all the individuals in a defined area that belong to the same species. Within this population of penguins, for example, we can study demographic characteristics such as age structure, sex ratio, birth and death rates, and immigration and emigration. We can also map locations of individuals within a population across a landscape and study how they interact with their environments and each other.

Environmental scientists use mathematical models based on non-human organisms to frame predictions about the future of our population. Human populations match some, but not all, aspects of non-human populations.