Sponges have cellular-level organization meaning their cells are specialized so that different cells perform different functions. On the other hand, these cells are not organized into tissues etc. This is the simplest form of organization. They have a system of pores for water to move through called ostia. They tend to be symmetrical. Their skeleton is made up of the protein collagen and spicules. They reproduce sexually and asexually. When they reproduce sexually it can be called spawning. When they reproduce asexually, it can be called budding.