Final answer:
Sponges are multicellular filter feeders with specialized cells called choanocytes that use a flagellum and collar to generate water flow and capture food. Adults are sessile while larvae can swim. The beating of the choanocytes' flagella is vital for the sponge's feeding, excretion, and gas exchange processes.
Step-by-step explanation:
Sponges are multicellular organisms that do not have mouths and instead filter feed by drawing water through tiny pores in their bodies. This flow of water is essential for feeding, excretion, and gas exchange. At the core of their unique feeding system are specialized cells known as choanocytes, or "collar cells." Choanocytes have a flagellum surrounded by a collar that maintains water flow through the sponge and captures and digests food particles. While adult sponges are sessile (non-motile) and remain attached to a substrate, sponge larvae are flagellated and capable of swimming freely.
Water Flow and Sponge Anatomy:
Sponges pump water into their body through pores and move it through a large central cavity called the spongocoel. The water is filtered by the choanocytes, which trap and digest food particles in the water. Then, water is expelled out of the sponge through an osculum, while oxygen is diffused into the sponge's cells and wastes are expelled. The beating of the flagella from all choanocytes is what moves the water through the sponge, a critical process for the sponge's survival and function.