In the formula $\frac{\text{dn}}{\text{dt}}=\text{rN}\left(\frac{\text{K}-\text{N}}{\text{K}}\right)\text{,}\left(\frac{\text{K}-\text{N}}{\text{K}}\right)$ stands for environmental resistance. Environmental resistance is the sum of the environmental factors (such as drought, mineral deficiencies and competition) that tend to restrict the biotic potential of an organism or kind of organism and impose a limit on numerical increase.