the maximum reproductive capacity of an organism under optimum environmental conditions. It is often expressed as a proportional or percentage increase per year, as in the statement “The human population increased by 3 percent last year.” It can also be expressed as the time it takes for a population to double in size (doubling time). In disease-related studies it is comparable to the “force of infection,” the number of susceptible individuals each infected individual further infects.

Full expression of the biotic potential of an organism is restricted by environmental resistance, any factor that inhibits the increase in number of the population. These factors include unfavourable climatic conditions; lack of space, light, or a suitable substrate; deficiencies of necessary chemical compounds or minerals; and the inhibiting effects of predators, parasites, disease organisms, or unfavourable genetic changes.