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Science        < Previous        Next >

 

Sponges

 

Today's Snack: How about an Edible Aquarium? Dissolve one 3-oz. package of berry blue Jell-O in cup of boiling water. Separately, combine cup cold water with enough ice cubes to make 1 cups ice water. Add the water to the Jell-O, stirring until slightly thickened. Pour Jell-O into four clear glass dessert dishes or small glass bowls. Place colorful gummy fish in Jell-O. Refrigerate for one hour before serving.

 

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After School Treats notebook and pen or pencil

Natural sponge (purchase from a bath boutique or borrow one?)

2 bowls

Water

 

 

You might think they're part of the underwater rocks. You might think they're an underwater plant. But nooooo! Even though they are more like rocks or plants because they don't move very much, sponges are animals. And if you thought Sponge Bob was "unique," you ought to see all the amazing variety in the colors, shapes and sizes of this plentiful form of life:

 

Go to fullsize image Go to fullsize imageGo to fullsize imageGo to fullsize image

 

 

There may be as many as 10,000 different species of the sponge, almost all in saltwater oceans and seas, but about 150 known species in freshwater settings. While the sponge might appear to be a very simple animal, actually there's a lot going on:

 

  • Sponges have two layers to their outer body that are connected by a layer of gel; inside each major structure of a sponge's body, most species have an inner cavity that water flows through

 

  • They have thousands of pores on their bodies that water flows through to provide them with food and oxygen. Tiny particles of organic matter are removed from the water by the sponge as nourishment. This is called filter feeding.

 

  • The sponge gets rid of the water after it extracts nourishment and oxygen through a large pore called an osculum, which means "door" in Latin.

 

  • They eat tiny organic particles that float through the water into and out of their bodies, extracting nutrition from them as well as oxygen from the water, even though they don't have a bloodstream or any muscles, tissues or bones.

 

  • Spikes on their outer surface to protect them from fish or other predators

 

  • Flagellum cells, like miniature whips, that move around and push water through the sponge

 

  • Spicules on the outside of the body, which are cells to help the sponge maintain its shape and prevent it from collapsing; they make a sponge feel kind of gritty when touched.

 

  • Even though they don't have brains, eyes and ears, if you touch many species of sponges, they will verrrrrrrry slowly "cringe," or pull back. This is thought to be some kind of a chemical reaction to stimuli, but scientists don't understand it well.

 

  • Sponges can communicate with each other, probably by releasing chemicals into the water, so that two sponges both release their sex cells into the water on the same day so that they can merge and form a baby sponge. They also can reproduce simply by having a part of themselves broken off; it might float away, reattach, and go on living as more or less of a clone of the parent.

 

  • They may live one year, or many years, and many species go dormant during the winter months. That means they don't eat or grow for a while, but act like they're asleep, 'til the water warms up and there's more food in the water again.

 

Sponges are invertebrates, which means they don't have a backbone. They also don't have a hard shell outside their body for protection, like a clam or a bug might have. But they do leave a skeleton when they die, and that is what we think of as a "sponge" to use in cleaning and bathing.

 

Quite a while ago, we found out that we could manufacture artificial sponges for far less money than we could harvest sponge skeletons from the ocean, so nowadays, almost all the sponges you see in the grocery and hardware stores for sale are fake sponges. You can usually buy a real one in a bath boutique, for example, and you will notice how its holes and openings are irregular, in contrast to manmade sponges, which have a consistent, obviously machine-made look.

 

Sponge bodies may be tubes, fans, cups, cones, blobs, barrels or a crust over something else. They may be green, orange and every color in between. There are sponges that look just like miniature volcanoes, and sponges whose outer surfaces look just like breadcrumbs. You mostly see them on the lower shore of an ocean in patches that are about a yard square.

 

What really sets sponges apart is that they are sessile, or stationary. They don't move. At the bottom of their body, they have body parts that are like fat tree roots, that together are called a holdfast that . . . well, fastens and holds them to the rock or whatever is their anchor down on the ocean floor.

 

Now here's a little experiment you can try:

 

Measure several cups of water and pour into one large bowl. Estimate how many cups of water you think the natural sponge that you have bought or borrowed for this activity will soak up. Then plunge it into the water and leave it there for a minute. Finally, lift it out, let it drip for a few seconds, and then transfer it over an empty bowl, and squeeze. Take your time and squeeze every drop of water out of the sponge that you can. Then measure how much water you got out of the sponge. Were you close, or 'way off? Isn't it amazing how the sponge can get its food, without lifting a finger?

 

Reminds us a lot of our KIDS!!!! Just kidding.

 

Now you know where the expression "sponging off" comes from!

 

By Susan Darst Williams www.AfterSchoolTreats.com Science 06 2008

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