Questions: Chapter 24 Question 28 - Multiple Choice Part A The currents of water (containing food) that pass through a sponge are maintained by the osculum. collar cells. ganglia. a water-vascular system. medusae.

The answer is the second one (B): collar cells.

Explanation for each option:

• The osculum: This is an opening in a sponge through which water exits, but it does not maintain the currents of water.
• Collar cells: These cells, also known as choanocytes, have flagella that create water currents and trap food particles, thus maintaining the flow of water through the sponge.
• Ganglia: These are clusters of nerve cells found in some animals, but they are not involved in maintaining water currents in sponges.
• A water-vascular system: This system is found in echinoderms (like starfish) and is not present in sponges.
• Medusae: This term refers to the free-swimming stage of certain cnidarians (like jellyfish) and is not related to sponges.

Summary: The currents of water (containing food) that pass through a sponge are maintained by collar cells.