But how much do you really know about sponges?
Sponges have no bones, eyes, teeth, nerves, blood, ears, or mouths!
They are really simple animals—about the simplest multicellular (many-celled) animals. They only have a few types of cells, with little specialization. Not like us. Really more like a colony than an organism.
They first appeared on earth in pre-Cambrian times, long before dinosaurs, land plants, fish, or most of the other creatures we see today.
They live on the bottom, where they attach themselves to something. As larvae they swim around. After they settle they can't move (no legs!).
They are "filter feeders". They catch and eat tiny animals and bits of floating food too small for us to see.
There are about 5,000 different types—all colors, forms and sizes. There are sponges six feet tall, big enough for a person to hide in!
Or how about a sponge spawning:
Most live in the oceans, though some live in fresh water
Sponges have sex! Most are "hermaphrodites", able to act as males or females (though not necessarily at the same time).
The scientific name for the group we call "sponges" is "Porifera"—cause they have pores, get it? Those "pore" sponges—they're "pore-ferated"!
"Sponge" in Spanish or Portuguese is "la esponja", in French "l'éponge", in German "der Schwamm", in Russian "губчатый", in Japanese 海綿 (かいめん), in Chinese 海绵.
Sponges have a reinforcing "skeleton" of protein fibers (spongin), calcareous (lime) spicules, silica spicules, a combination of these, or perhaps no skeletal structure at all. Commercial natural sponges that you might use in the bath have all the living tissue removed—all that is left is the skeletal material.
Most sponges you buy in the store are synthetic, made from foamed cellulose, rubber or plastic. This helps prevent overharvesting of natural sponges. Loofahs are not sponges either, but the cellulosic skeleton of a type of gourd similar to a zucchini!
Here are some links for more information: