- a polysaccharide gel and dead cells.
- a collagen-like gel and suspended cells for various functions.
- spicules composed of silica or calcium carbonate.
- multiple pores.
The large central opening in the parazoan body is called the:
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.