Grades 6–8 · Organisms
How can a sponge feed while staying attached to one place?
A living sponge does not need to chase every piece of food. Water enters through many small pores and travels through internal passages. Suspended microorganisms and other suitable food can be collected as that water passes.
In the diagramFlagellated cells drive water through a spongebody channelcollar cell + flagellum
Specialized cells called choanocytes have beating flagella, slender moving structures that help create the flow. A collar around each flagellum traps small particles. Cells then take in food and process it.
The water also brings dissolved oxygen and carries away wastes. It leaves through larger openings after moving through the body’s channels. The sponge therefore depends on organized internal flow rather than a heart pumping blood through vessels.
Its body shape provides a large interface between cells and moving water. Different species arrange channels in different ways, but pumping and particle collection remain closely connected. An apparently still animal can be carrying out continual microscopic work inside its porous body.
About this explanation
Starting knowledge: Recognize that tiny food particles can be suspended in water and that coordinated cell movement can create flow.
Sources
- NOAA Office of National Marine Sanctuaries — Barrel Sponge