Most of our food comes from agriculture, so we tend to believe that it is ________ (6) of natural biota. This is not true. In nature, ________ (7) plants and animals ________ (8) to the rigours of natural selection. Only the fittest survive. ________ (9) wild populations have numerous traits for competitiveness, resistance to parasites, ________ (10) to adverse conditions, ________ (11) other aspects of vigour. In contrast, populations grown for many ________ (12) under the pampered conditions of agriculture tend to lose these traits, because they ________ (13) for production, not resilience. For example, a high-producing plant ________ (14) lacks resistance to drought is ________ (15) and the resistance to drought is ignored. Also, in the process of breeding plants for maximum production, all genetic variation is eliminated.