Large numbers of escaped plants may become a noxious weed. The adaptive and ecological variables seen in plants that go wild closely resemble those of animals. Feral populations of crop plants, along with hybridization between crop plants and their wild relatives, brings a risk that genetically engineered characteristics such as pesticide resistance could be transferred to weed plants.[4] The unintended presence of genetically modified crop plants or of the modified traits in other plants as a result of cross-breeding is known as "adventitious presence (AP)".[5][6]