Galapagos tortoises are certainly not the only organisms that show variations. Describe variations you have observed among another group of organisms, like plants, butterflies, birds, or fish.
Among the species of organisms Darwin have observed, another group are birds. Birds that have short,tough beaks consumes seeds and grains like pigeons while those that have long, tough beaks use it for nectar-feeding like hummingbirds. Also those that have thin, sharp beaks use them for feeding on insects or other prey like pelicans.