Fish

More than 22,000 different species of fish live in the oceans, lakes, and rivers of the world. Fish come in all shapes and sizes. Some eat water plants, some eat other fish. Lampreys and some jawless fish suck onto other fish for food. Stone fish live on ocean bottoms and camouflage themselves as rocks. Puffer fish blow themselves up like a balloon, only they’re covered with spines. There are tons of strange and cool-looking fish everywhere.

Fish descended from the very first animals with backbones on Earth, sea animals called ostracoderms. Animals with backbones are called vertebrates. That includes you and me, pal. Fish backbones are important because fish use muscles attached to their backbones to swim. Fish breathe underwater with gills, layers of feathery delicate membranes, usually behind their eyes. A fish’s gills absorb oxygen dissolved in water and release carbon dioxide. The same way your lungs absorb and release oxygen and carbon dioxide in the air we breathe. Gills collect oxygen in water and let out carbon dioxide. Since fish are in almost every lake, ocean, river, and pond, it’s important to keep water clean to make sure fish have a clean place to live.

The “Fish” episode will get you hooked on science.

The Big Ideas

• Fish have backbones.
• Fish breathe underwater.
• Fish live almost everywhere there is water.

Did You Know That?

• Fish in very cold waters have special “anti-freeze” chemicals in their bodies?
• One of the fastest fish is the sailfish? It has been clocked at 109 kilometers (68 miles) per hour.
• Black “swallower fish” can gulp down other fish twice their size?

Books of Science!

• “Bill Nye The Science Guy’s Big Blue Ocean”by Bill Nye (I’m proud of it!)
• “Eyewitness Juniors Amazing Fish” by Mary Ling. Published by Alfred A. Knopf, 1991.
• “Fish” by Michael George. Published by The Child’s World, 1991.