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]

I really like this Glen and plan on using it in my classes- both 9th and AP. I like eco pyramids but I have found some students don't quite get the transfer even though for me it seemed obvious. This definitely makes them remember even though they may be saddened in the end that they don't get any root beer! (Actually I feel most sorry for the one that gets just .1ml!) The other cool thing about this is that it totally reinforces metric and visualizing/estimating sizes.

[Glen Westbroek]

Debra,

I started this a couple of years ago and found it caught my student's attention quickly. I also liked the metric tie-in. While we did estimate how much each person would get, I did not even think about that being part. Thanks for reminding me of it.

I ask for volunteers and usually select the order they get the root beer in. (Not in any mean way - just so I make sure it's not someone who would break down at .1 ml.)

[Debra Garcia]

Wanted to let you know that I did this w/ my AP class and they loved it even though it was really simple. They also let out a huge sigh when I poured the rootbeer down the drain.

[Glen Westbroek]

Glad to hear it went well (even if simple). The sigh to me signifies understanding of the concept!

[Debra Garcia]

And when I wrote simple- I meant it in a good way. Simple meaning that sometimes folks think AP needs to be so intense, so advanced. Or that they should also just get it by looking at a book diagram and breeze past that concept. Activities like this are awesome! Being able to explain a topic in simple terms is the best thing ever- isn't there an Einstein quote about that? Something like if you can't explain something simply, you don't understand it well enough?

Food and equal sharing always seems to hook students. I had mentioned to them that they might get root beer in class for an eco demo over a week ago. They saw the cups on my lab bench and said "Is that for the root beer activity?" I thought...They remembered I said that? I did give them the other part of the two liter drink if they wanted it. ( I only have 10 kids in AP)

[David Williams]

Thanks for posting this. I'm teaching energy transfer at present to Y9 and feel that we have got bogged down in the details of the ways energy is lost between levels. The result is that the overall message that higher levels actually get much lower amounts has been lost a little. Now I'm going to use your activity to reinforce this.

[Glen Westbroek]

David,

I gave my students a quiz on Trophic levels on Friday and as thrilled that over 85% of them remembered only 10% of the energy is passed on to the next level. (The question was free response so I could see all student thinking.) I'm not convinced this is the "Best" way to teach the concept, but it is nice to see them comprehending it after several weeks.

[Colin Matheson]

I like this as a good hook for discussion. I use a warmup question "Why don't we eat mountain lions?" to get kids thinking. I still have trouble getting the kids to understand why the energy is "going away". Also they tend to think that there is more energy in a specific herbivore when compared to a carnivore, instead of more energy at the whole level. Thanks for sharing.

[Heather Kiegel]

This is an awesome idea to help students visual an otherwise abstract concept. I am looking for ideas like this as I am working on a certificate to teach English learners.

[Glen Westbroek]

Heather,

From experience, I agree that this helps English learners due to the visualization. It's important to find methods that can help all students comprehend concepts like this. Good luck in your English Language Learners certification.