The evolution of herbicide resistant weed populations is an inevitable consequence of the selection pressure imposed on the weed community by the use of weed management tactics that focus on herbicides. Weed populations typically demonstrate variability in response to herbicides. Some individuals of the weed populations are extremely sensitive to a specific herbicide while other individuals require considerably more herbicide for control. Herbicides that have a single place (gene loci) in the plant in which the toxic response is elicited (mechanism of action) are more likely to quickly evolve resistant weed populations. However, it is possible, given the genetic diversity in weed populations, polygenically controlled resistance can ultimately evolve over time.