As the size of some animals has evolved to greater sizes, the effectiveness of their adaptations that promote exchanges with the environment have also increased. For example, in many larger organisms, evolution has favored lungs and a digestive tract with?

More branching or folds.

Explanation:

Adaptation may be defined as the ability of the organism to adapt and survive according to its environment. Physical, physiological and chemical changes occur in the body of organism for the adaptation process.

The evolution of the increase in the size of the animals might also changes their internal physiology. The lungs and digestive tract also evolved as the size of the organism get bigger. The lungs has the alveoli to increase the surface area and inhalation of more oxygen in the body. Digestive system has villi or folds that increases the surface area for digestion and absorption.

Thus, the answer is more branching or folds.