Most sponge body plans are slight variations on a simple tube-within-a-tube design. which of the following is a key limitation of sponge body plans?
sponges lack the specialized cell types needed to produce more complex body plans.
the reliance on osmosis/diffusion requires a design that maximizes the surface area to volume ratio of the sponge.
choanocytes must be protected from the hostile exterior environment.
spongin cannot support heavy bodies.