Biotic Balancing Act

[45 Minutes]

Have you ever played on a see-saw or teeter-totter? Wasn’t it more fun when the playmate on the other side was about your size and weight? If either of you was much bigger or heavier than the other, it was probably not much fun, or maybe even unsafe. Nature works in much the same way. Our environment likes to remain in balance. We’re going to create our very own biotic community,, so that we can see how much living things really need each other to survive.

You'll need:

• a five gallon jug-like glass container • a large cork that fits in the opening of the jug • sealing wax or paraffin • small pebbles and sand • aquarium style plants • water • one goldfish • water snails • one long stick, the length of the jug

What to do:

1. If possible, print out these directions. Read them through with your child before you begin.
2. With your child, gather everything you’ll need.
3. Help your child fill the jug with water until it is 3” from the top.
4. Let your child add pebbles and sand to cover the bottom of the container.
5. Together with your child, use the stick to secure plants in the sand and pebbles, letting the rest of the plants to float freely.
6. Together, let stand and observe. Let this sit for 24 hours.
7. After 24 hours, help your child place the snails and goldfish in the container.
8. Assist your child in placing the cork in the top of the jug, sealing it with wax or paraffin.
9. Together, place the container near a window and observe.

Let's Talk: Ideas to Explore Together.

• How would your biotic community be different if there weren't any plants?
• What would it be like if you used many large fish?
• What do think is the source of oxygen for the goldfish?

Useful information:

Guess what? You may not have noticed, but you learned something very important by doing this experiment. All living things in a certain area form a biotic community,. They obtain, from each other, what they need to continue living. There are three types of living organisms in any biotic community: producers, consumers, and decomposers. Basically, producers make what consumers need to live, and decomposers change plants that have died into nutrients, so that it can all start all over again! In your biotic community, plants gave off oxygen during the daytime and took in carbon dioxide. The animals gave off carbon dioxide and took in oxygen! Didn’t that work out nicely? Just like riding a see-saw with your best friend!