As animals attained larger and more complex bodies, exchanges with the environment became more difficult. Describe the problems of larger bodies and the solutions that solved these problems but led to increased complexity. Consider advances of Porifera, Cnidaria, and Platyhelminthes and include in your answer:

a. a description of surface-to-volume relationships as applied to animal growth.

b. adaptations and behavior that allowed better exchanges of oxygen and carbon dioxide.

c. structural modifications that allowed better processing and distribution of food.

d. the advantages and disadvantages of mesoderm, the necessity of modifications for the elimination of nitrogenous waste, and a description of protonephridial function