A graph in which the number of organisms in a population is plotted against time. Such curves are amazingly similar for populations of almost all organisms from bacteria to human beings and are considered characteristic of populations.

Growth curves typically have a sigmoid or S-shaped curve. When a few individuals enter a previously unoccupied area, growth is at first slow during the positive acceleration phase. The growth then becomes rapid and increases exponentially, called the logarithmic phase. The growth rate eventually slows down as environmental resistance gradually increases; this phase is called the negative acceleration phase. It finally reaches an equilibrium or saturation level. The final stage of the growth curve is termed the carrying capacity of the environment.

A good example of a species' growth curve is demonstrated by the sheep population in Tasmania. Sheep were introduced into Tasmania in 1800. Careful records of their numbers...