Sponges are invertebrate ANIMALS!!!
Yes, believe it or not, they are not just pretty plants
growing at the bottom of the sea. Sponges are actually the simplest form of multi-cellular animals. They live on the bottom of the ocean floor and hopefully find a location which provides a good source of food for them. They can sometimes develop into an “apartment building” for many organisms, and often can be used as a “fortress” for them when a predator is in the area. Sponges are very important to ocean animals, and as recent information has hinted, they many become much more important to humans also.
Sponges belong to the phylum Porifera. There are four major groups of sponges that exist. The Calcarea are marine sponges with skeletal spicules containing calcium carbonate. Then, there is the Hexactinellida which are found in the deep seas of the world, this is the side of the family that got all the “looks”. Their skeleton is made of silica (a substance used to make glass) and they come in many different beautiful colors, they are often referred to as the glass sponges. The Sclerospongiae are the complicated side of the family, they are made up of thin silica and a spongin skeleton that surrounds a large, central calcareous skeleton. Finally, there is the “abnormal” side of the sponge family that no one wants to talk about, the Demospongia. This family contains the few freshwater cousins, and is the largest family connection making up about 95 percent of all living species. They are made up of a flexible protein material, similar to that of a bath sponge. This side of the family contains the dreaded, feared relative, the Mediterranean sponge, which is a carnivore.
Sponges are further separated into two different groups based on their method of growth. The encrusting sponges usually cover the surfaces of rocks, similar to the moss found covering a rock or tree. And, the fffffreestanding sponges grow into different shapes and can grow into gigantic sizes. The freestanding sponges are usually the most recognized because of their size, colors, and sometimes strange shapes.
All the major groups of sponges existing today are also rumored to have been living in the Cambrian period, some 600 million years ago. In fact, some scientists believe that the sponges may share a common ancestor with jellyfish and corals.