Trophic Levels and Energy Transfer

[Glen Westbroek]

Today’s objective dealt with understanding the 10% rule of energy transfer between trophic levels.

I used four student volunteers. They represented Producer, Herbivore, Carnivore, and Scavenger.

Started with 1 liter of RootBeer in LARGE Graduated Cylinder. Poured out 100ml for first student (producer). Removed 10 ml from this for second student (herbivore). Took 1 ml out for third student (carnivore). FInally removed 0.1 ml using a pipette for fourth student (scavenger).

Poured Root Beer from the graduated cylinders I used into plastic glasses. I then allowed students volunteers to drink their respective cups. As students drank their liquid, the class discussed why not all of the energy is passed onto the next trophic level. The class then noticed that I still had 900 ml left in the large graduated cylinder. There were empty plastic glasses on the counter. Expectation was high to share in the wealth! I then discussed how the sun’s energy does not all fall on plants. I reminded students that some energy hits rocks, soil, and water. Much of the energy escapes at night as Earth cools. During this part of the discussion, I poured ALL of the 900 ml of RootBeer down the drain in my classroom sink. There was a LOUD outpouring of grief - but based on the questioning at the end of class, students comprehended the fact that a LOT of energy is lost during transfer between trophic levels.

I’m interested in hearing what “engaging activities” you use with students to help them grasp difficult concepts.

[Debra Garcia]

Another year of success with this activity.

Next year I may just throw in vanilla ice cream at the end for a secret rootbeer float surprise (dumping the main stuff down the drain but have a secret 2Liter bottle available.) Thanks again for this.