Re: Why are sponges classified as animals and not as a colony of protists?

Sponges are the closest animals to protists, and as such lack many of the features of animals. Infact there are some protists that on the surface look very similar to sponges. But although a few protisits are able to form multiclellular structures that look like sponges and behave like sponges they are capable of surviving unicellularly. If you took one of these protists and gentely mashed it so as not to lyse all the cells, the cells would survive and eventually form another sponge-like colony. The sponge would die if you did the same thing to it. So the sponge is truly multicellular and thus has to be a fungi, plant, or animal. The sponge is a filter feeder and thus can not be a plant or a fungi. Each of the many filters can be viewed as a gut, the filter cells absorb the food, and then the amoeba cells take the food from the filter cells to the other cells in the organism such as the epithelial cells. I hope this answers your question