Structure and Function: Sponges belong to the phylum Porifera, and are very simple creatures. They possess no organs or digestive tract. There is no symmetry or segmentation. The way these creatures reproduce is asexual by budding.
Ecology: Some sponges are big, and can be protection for other animals. For example, the barrel sponge has a large hole in the middle. Many animals will use this cavity for shelter Most sponges are also covered in algae. The sponges provide shelter for the algae, and the algae provides the sponge with food.