Sponges do not have nervous systems, so they don't react to the world around them. Sponges are really just a bunch of specialized cells working together to help the entire organism survive.

Once the larvae land on a piece of rock, they take root (so to speak) and that's that, forever anchored. Baby sponges don't look like adult sponges, so scientists use another word. The word larva is another way to describe them when they are babies. There was a time in their lives when they were little larvae that they were swimming around the water all by themselves. Most sponges live their lives attached to a reef. There are two basic forms in the life cycle of a sponge. When we talk about sponge structure, remember all the holes. You may have even seen a couple around your bathtub! The ones around your bathtub might look like sponges but they are usually man made. Most sponges are found in seawater, only a few in fresh water. They are so basic that they have not developed many of the characteristics you might think of when you think of animals. Sponges - The First Invertebrates Sponges are kind of like the exception to the rules of invertebrates.

Water moves through sponges