Q. As animals attained larger and more complex bodies, exchanges with environment became more difficult. Explain the problems of larger bodies and the solutions that solved these problems but led to increased complexity. Think about the advances of Porifera, Cnidaria, and Platyhelminthes and include in the answer-

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

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

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

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