The ancient sponge appeared about 2.5 billion years ago—the first animal. Coming in many sizes and shapes, sponge bodies are a loose assemblage of cells held together by a special protein called collagen which is present in all animals. In addition, sponges have microscopic crystalline spicules that act as a skeleton. We see an animated view of the incredible variety of shapes of these spicules. Sponge cells carry out all the functions that organs carry out in higher animals and they communicate with each other, an ability all animal cells share. Sponges are the only animals that if broken down to the level of their cells, they can reassemble themselves. Dr. Cristina Diaz demonstrates how quickly sponges filter water to obtain food by injecting a colored dye just outside the sponge and watching how quickly the sponge pumps out the dye. We go on a wild ride inside the sponge through holes, tunnels and chambers. Sponges also use their pumping to reproduce: they pump sperm and eggs into the water. They were the first animals to reproduce sexually.
Next Generation Science Standards for this Video
Sponges don’t have tissues and organs. The beating choanocyte cells (specialized cells with flagellae) and the porous structure of a sponge’s body are adapted to pump water throughout its body. This brings food to all the sponge’s cells.
Even though mutations in genes affect traits, fundamental core genes tend to be conserved throughout the animal kingdom. Those genes that control the sponge’s multicellular way of life got passed down through evolution to all other animal life.