The Five Basic Life Functions of a Sponge

Movement

• Sponges are sessile creatures, meaning that they lack any mode of self-propulsion. However, some types sponges move themselves unintentionally as water passes through their bodies for excretory and digestive purposes, propelling them in some direction. Though the main cause of the transportation of a sponge from one place to another is the underwater current, a sponge is typically anchored to the ocean floor, so it remains stationary for the bulk of its lifespan.

Food Ingestion

• Sponges lack a standalone digestive system. As fresh water flows through a sponge's body, tiny, tail-like protrusions called flagella, which line the internal walls of the sponge, constantly wave to keep water flowing through the sponge. As water flows through a sponge, minerals and necessary bacteria are absorbed, providing it with nourishment. This method of ingestion is called "filter feeding."

Excretion

• As water is constantly forced through the body of a sponge by its flagella, waste products are carried away by the flowing water and is expelled from the sponge through a large opening called the osculum. The osculum forces water outward at more than 3 inches per second, causing the waste products to disperse into the surrounding water and float away from the sponge.

Respiration

• Sponges lack real respiratory organs such as a heart, lungs and even blood. Instead, sponges use water to deliver oxygen to its entire body. In essence, the current of the water and the waving motion of a sponge's flagella act as its "heart," forcing the "blood" (water) through the sponge's body, where oxygen is absorbed from the water directly into the tissue of the sponge -- the sponge's "lungs."

Reproduction

• Sponges can reproduce themselves through three separate methods. Most sponges are hermaphroditic, meaning that they contain both male and female reproductive organs. Sponges reproduce sexually by releasing sperm into the ocean's current, which then floats until it reaches and fertilizes another sponge. Sponges reproduce asexually by growing "buds" that eventually fall away and grow to become new sponges. Another method of reproduction peculiar to sponges is called "fragmentation." If a piece of a sponge is broken off, not only does the sponge regenerate its lost body part, but the broken piece also grows into an entirely new sponge.