Sponges contain specialized cells like choanocytes that use flagella to move water through the sponge for feeding, respiration, circulation, and excretion. They have structures like spicules made of calcium carbonate or silica that form their skeleton, and archaeocytes that produce these spicules. Sponges reproduce through internal fertilization and larval stages, and some can form protective gemmules during unfavorable conditions.

1. 26.2 Sponges

2. Choanocyte
• Specialized cell in sponges that uses a
flagellum to move a steady current of water
through the sponge.

3. osculum
• Large hole at the top of the sponge through
which water leaves the sponge

4. Spicule
• Spike-shaped structure that makes up the
skeletons of harder sponges; made of either
calcium carbonate or silica.

5. Archaeocyte
• Specialized cell in a sponge that makes
spicules

6. Internal fertilization
• Process in which eggs are fertilized inside the
female’s body.

7. larva
• Immature stage of an organism that looks
different from the adult form.

8. Gemmule
• Group of archaeocytes surrounded by a tough
layer of spicules; produced by some sponges.

9. Key Concept
• Sponges are classified as animals because they
are mulitcellular; heterotrophic, have no cell
walls, and contain a few specialized cells.

10. Key Concept
• The movement of water through the sponge
provides a simple mechanism for
feeding, respiration, circulation, and excretion.