As animals have evolved large body size, they have also evolved adaptations to improve exchange of energy and materials with the environment. for example, in many larger organisms, evolution has favored lungs and a digestive tract with as animals have evolved large body size, they have also evolved adaptations to improve exchange of energy and materials with the environment. for example, in many larger organisms, evolution has favored lungs and a digestive tract with decreased blood supply increased thickness more branching or folds larger cells