Biomagnification

Age

Elementary School, Middle School, High School

Format

Stage, Hands-on

Materials

   Plastic cup
   Red marbles
   Clear marbles (in biomagnification box) 

Safety Precautions

Science Theatre demonstrators must keep the safety of themselves and their audience in mind at all times. All Science Theatre demonstrators must have read through the Safety Training page. The ST Safety Box with first aid kit, fire extinguisher, etc. should always be available to demonstrators. Always wear safety gloves, glasses, and a labcoat if handling chemicals; always perform potentially dangerous demonstrations at a safe distance from the audience; and always keep a very close eye on any volunteers you call from the audience. Don’t let small children (or large children, or small or large adults) eat the marbles.

Preparation

Set up enough cups for children participating in the demonstration, designate most of the kids to be minnows, some kids to be fish, and only one to be the shark. The minnow cups should have a few red marbles and one or two clear marbles. Fish and sharks only get a few clear marbles.

Demonstration

Start out by showing each cup. Only the minnows have been contaminated (it could be from mercury or something similar in the water) and contain clear marbles. Everyone else only has red (uncontaminated) marbles.

Spell out the rules. Minnows just swim around. Fish eat minnows, and sharks eat fish. To eat someone else, you just take the marbles from their cup.

Allow kids to eat each other

Once the shark is the only one left alive, show everyone what is in his cup. One or two clear marbles are okay, and the fish can survive, but the shark will have a lot more than one or two. Explain how this works in real life, and introduce the term biomagnification.

What to Say

Has anyone ever heard the word “biomagnification?” It’s what happens when we pollute our environment, and can be very bad for us! We have a demonstration today that will teach all of us what biomagnification means! (If this is a stage show, ask for volunteers; otherwise assign roles to each kid. You should have one shark, at least two fish, and four minnows. Any number of kids should work; just try to arrange it so that there are a lot of minnows and a few fish and one shark.)

After they complete the activity, show them the contents of the shark’s cup (they should have all the marbles.) Explain that while one clear marble is not toxic, this many are. The shark would probably die because of the high concentration of toxins. Explain how this is very common with mercury in our water, and other environmental pollutants. That’s why it’s so important that we don’t pollute! We may end up eating an animal that has a large buildup of toxins.

Why It Is

Because predators often eat more than one animal, if a toxin cannot be removed from the body naturally, it will build up. If they continue eating animals that are contaminated (or worse, animals that have eaten animals that are contaminated) they may accumulate a very high amount of toxins.

Real Life Examples

Mercury and other heavy metals, DDT (see Rachel Carson’s Silent Spring) All of these have been found to accumulate in organisms and then have the potential to biomagnify.