Skip to Content

Ecosystems | Activity 3.5

Activity 3.5: Tracing Energy Through an Ecosystem (30 min)

The previous activities showed how carbon atoms are “lost” from organic carbon to CO2 by all the organisms in ecosystems. In this activity students are reminded of why organisms need to lose carbon atoms: They need to use the chemical energy in organic molecules. All carbon-transforming processes use chemical energy for some cell functions; then lose heat to the environment (this heat is ultimately radiated into outer space). Thus, matter cycles; energy flows in ecosystems.

Resources Provided


Set up a computer and projector for 3.5 Tracing Energy PPT. You will also need to remind students about the movement of twist ties in Activity 3.2 Carbon Dice Game to solicit their initial ideas about energy flow in an ecosystem. Print out one copy of 3.5 Tracing Energy Worksheet for each student.


1. Use the instructional model to show students where they are in the course of the unit.

Show slide 2 of the 3.5 Tracing Energy PPT.


Use 3.5 Assessing the Tracing Energy Worksheet to get a sense of students’ initial ideas and explanations about tracing energy. At this point, students should not be penalized for incorrect ideas, and they should not be given the “correct” answers. This worksheet can be used for a formative assessment of student ideas about energy. Pay close attention to how students describe the movement and transformation of energy: in their explanations, do they ever break the “rule” by suggesting that energy is created or destroyed? Make sure to point out the rule: energy lasts forever!


For this activity, you will need to revisit some materials from previous activities: Activity 3.2 The Carbon Dice Game.

Extending the Learning

Have students discuss the difference between the way we talk about energy in an ecosystem (as light energy, chemical energy, and heat energy) and the way we talk about energy in casual conversations.