Population

In nature we rarely, if ever, find isolated single individuals of a species. Organisms live in groups occupying a well-defined geographical area, sharing or competing for similar resources, and potentially interbreeding with one another -- together these individuals constitute a population. Although it is always the individual organism that has to cope with changes in its environment, it is at the level of the population that natural selection actually operates to shape and pass on desirable traits across generations. Population ecology is therefore an important branch of ecology, because it links ecology to population dynamics, genetics and evolution as a whole. A population has certain attributes of its own that an individual organism simply does not have -- an individual has a birth and a death, but a population instead has a birth rate and a death rate. The two most basic physical characteristics …