Georgine Gambler, age 10, of Bethlehem, Pa., for her question:
Is a sponge an animal, mineral or vegetable?
Most people think that Everything around us must be animal, mineral or vegetable. Animals and vegetables, of course, are living things. As a rule, we can tell which is which. But all living things are built from assorted minerals, and the minerals themselves are non living things.
A sponge starts out as a living thing, and like all other living things it is built up from an assortment of non living minerals. It dwells on the ocean floor and if you went deep sea diving down to see it, chances are you would say that it is a plant. It looks for all the world like a chubby little bush, and around it other sponges seem to be rooted like the plants of an underwater garden.
But the sponge is not a plant at all. It is an animal. However, even experts admit that it is one of the Earth's oddest animals. There are things about it that make it very different from all other animals in the world. The strange sponges have no heads and no hearts, no limbs and no internal organs in their bodies. They come in different shapes and sizes, but all classed by themselves in the animal phylum Porifera.
Porifera means the pore bearers. And the living sponge has pores and more pores that riddle like tunnels through his entire body. He has a skeleton that may be stiff or rubbery and the skeleton is covered with thick, soft layers of flesh. The countless pores form a network of tunnels through the flesh and the skeleton.
Being an animal, the sponge needs food and oxygen. But he can make his living without taking a step or making a move. The surrounding water Enters his pores and tiny hairs keep it circulating through the inside tunnels and chambers. And the water carries with it oxygen and morsels of food, Scraps of algae and fish food are digested in some of the little chambers and oxygen is absorbed through the walls. The little hairs wave the used water mit through a large central tunnel and fresh water enters through the smaller pores.
A sponge may start life as an Egg or as a bud on the body of its parent. In order to grow, it takes food and minerals from the water. The sponge WE use to wash the car is the skeleton of an ocean animal, stripped of its f1esh. The skeleton is made of spongin, which is a mineral.
Most sponges live in the sea, but a few of the small fellows Enjoy life in fresh water lakes and rivers. Some types look like vases or flower pots, some are like flowers or fancy fans. Some have hard skeletons made of calcium or glassy spikes. A few have leathery skeletons of spongin that often End up as squeezeab1e bath tub sponges.