Humans have been performing artificial selection for thousands of years with breeding dogs, growing particular crops and raising cattle. In artificial selection, breeders select parent organisms with desired characteristics, in the hopes that when they are crossed, the desired variations will appear in the offspring. In natural selection, organisms reproduce sexually. The offspring contain a blending of both parents' DNA. In a certain environment, particular variations may prove to be beneficial to survival. If the organism is "fit" it does survive and reproduce, thus possibly passing its traits to future generations. In this case, the environment or nature decides which traits are best adapted. An example is coloration. If an organism naturally blends into its surrounding, it avoids predation. If another of the same species has a color that stands out, it would probably be consumed by a predator. In this case nature selects which trait is best for a particular environment. In artificial selection, a person is doing the selecting.