Food Chain Game

Investigate food chains by assuming the roles of animals that are part of a food chain.

Group Size: 12 – 40

Suggested Age: 9 and up

Time: 30 min for activity + 10 min debrief + travel time to site

• Site: open space with designated boundaries
• Safety: No special considerations
• Prep: Materials- popcorn, three colors of sashes/signs and bags for stomachs.

Focus question:

What population sizes of grasshoppers, frogs and hawks produce a balanced food chain?

• In a balanced food chain, population size decreases as you move up a food chain from producer to highest predators.
• Imbalance with one population can dramatically affect the survival of other populations within a food chain.

Summary:
The transfer of food from one organism to another is called a food chain. This transfer takes place when one organism eats another, beginning with a plant or producer. While participating in the Food Chain Game, students modify the rules after each round based on their personal experience as predator/prey, naturally resulting in appropriate population sizes for each level. The food chain in this game consists of four links: plants → grasshoppers → frogs → hawks. A population is a group of organisms of one kind that lives in the same area. Popcorn represents the plant population, and the children play the parts of the grasshoppers (eat only plants), frogs (eat only grasshoppers), and hawks (eat only frogs). With each round, players are able to change the number of each population and create rules that mimic the real world. Download the folio for further specifics!

Extension:
“Bioaccumulation”
1. Replay the game with “poisoned” plants
Once you have balanced the populations in the food chain, throw some colored popcorn (caramel corn works well) into the mix with the regular popcorn. Do not tell the children what this signifies. Then repeat the final round. This works best if frogs place entire grasshopper stomachs (bags) inside theirs and likewise for the hawks when “eating” frogs.

2. Return to the classroom and dissect your hawks
Return inside with the final surviving stomachs and “dissect” your hawks for the class by pulling out the frog stomachs and then dissecting the frogs, keeping track who the stomachs came from.

3. Track the poison as it accumulates up the food chain
Now track the movement of the “poison” (colored popcorn) through the food chain. Draw a schematic noting the number of poisoned plants within each grasshopper, then the combined amount within that frog and the combined frog concentrations in the hawk.
Looking at this diagram, can you explain how bioaccumulation occurs within a food chain?

4. Bioaccumulation in Nature
Who does bioaccumulation affect most in the food chain? [top predator]
What are examples of bioaccumulation in the real world?
- DDT in insects affected the egg production of birds (especially raptors like hawks and eagles). This problem prompted Rachel Carson to write Silent Spring.
- Mercury from filter feeders accumulates in fish populations. Does not affect fish, but can be harmful to humans if we eat in high quantities.