Matter and Energy: Around and Around in the Chihuahuan Desert
By Stephanie Haan-Amato
Doesn’t everyone want to go back to high school again? We do!
The Asombro staff is excited to head into all of Las Cruces Public School high schools this year with a brand-new lesson about energy and matter cycling for 9th and 10th graders. This three-dimensional lesson is fully aligned with the Next Generation Science Standards (learn more about 3D learning in our blog post here). It meets the Performance Expectation: Use mathematical representations to support claims for the cycling of matter and flow of energy among organisms in an ecosystem.
In this ecology-focused, quantitative lesson, students start out with a hands-on activity right away. Without being told what they are making, students are given a scaled number of colored, small foam cubes and a key to show which colors represent which desert organism. They discover the bag contains 100 green for honey mesquite, 10 blue for jackrabbit, and 1 yellow for coyote.
We ask students to arrange their cubes in a logical way that makes sense to them. Sometimes, they end up making a trophic pyramid (or a trophic wall, a trophic tower, or a trophic blob). Sometimes, they simply sort them by color. However they arrange them, students realize that they are working with materials that represent a food chain.
This brings us to the central question of the lesson:
Why is there only one yellow cube?
In other words, why isn’t there as much coyote biomass in the Chihuahuan Desert as there is jackrabbit biomass as there is honey mesquite biomass? We spend the rest of the lesson delving into this question.
Students develop two more models, using actual scientific data (including some collected at the Jornada). They move multi-colored and -sized pom poms to represent different amounts of matter and energy. Using cards to prompt them with the transfers, students cycle their matter and energy around a trophic pyramid modeling board and keep track of the movement with wet erase markers.
While completing the physical model with pom poms, student also record the number of matter and energy in each transfer on a trophic pyramid model on their worksheets.
The lesson concludes with students measuring the matter transfer in the respiration of decomposers. After making a prediction, students use carbon dioxide sensors and data loggers to track the carbon dioxide levels. Students love learning that soil respires too, just like them! Well, almost.
The end of the lesson helps students tie everything together to make sense of the central question: Why is there only one yellow cube in our first model?
After moving matter and energy around the ecosystem, students have shown that most of the matter and energy in the system is transferred to the atmosphere through respiration and thermal energy transfers. Matter and energy leave the food chain constantly so coyotes do not have as much matter and energy available to have the same size population as jackrabbits or honey mesquite. Just like that – we have helped form amateur ecologists!
It is only the beginning of October, and we have already been able to bring this lesson to hundreds of 9th and 10th graders at Mayfield High School and Las Cruces High School. Students have impressed us with their intellect and curiosity and with how much they already know about energy and matter (maybe with the help of some Asombro lessons from middle school).
Some high school students are bringing up questions about population dynamics and are even tying humans into the ecology equation. We will be visiting Oñate High School and Centennial High School with the lesson very soon and are most definitely looking forward to it!
Stephanie is a Science Education Specialist with Asombro. As a former high school biology teacher, she is excited to be back in high school classrooms.