Dynamic Relationships in Ecosystems

By: Renata Martin and Neil Cashman, Middle School Science Teachers
Sixth grade science students just wrapped up their study of interdependence through the lenses of population ecology, community ecology, and ecosystem dynamics.
Following our study of the water and nitrogen cycles, sixth graders dove headfirst into looking at how energy is cycled and recycled between organisms, the importance of symbiotic relationships (commensalism, mutualism, and parasitism) to a community, and the nature of competition for resources in an ecosystem.

All year, the sixth graders have been practicing organization habits including the organization of information — yes, those Cornell notes middle school families have probably heard so much about! The first two trimesters, we practiced using the Cornell Notes system which is a very structured style of note-taking. Finally, with all that practice under their belt, the students explored other types of note-taking — outline, boxing, chart, mapping — to gather information for this unit from a curated selection of videos and our science textbook.

Once they’d gathered information, the sixth graders put their learning to the test by conducting an online simulation of population dynamics. Starting with an experimental question following a structure like, How does the prey population affect the plant population? students wrote a hypothesis relating to their question: If I change the prey population to 1500 while keeping predators at 50 and the whole ecosystem dies it means that there are too many herbivores for the number of plants. This way they could test their understanding of the relationship between species in their ecosystem. They wrote out their own procedure, conducted trials, and charted their data. Then, they analyzed the data by looking at line graphs to explain why their results occurred, and then finally, wrote their conclusion — or, the answer to their initial experimental question.

Finally, to synthesize their learning, students created their own Utopian Ecosystems to explore this unit’s guiding questions: How is energy exchanged in a community of organisms? How do organisms coexist? How do they impact each other? How do organisms compete for resources in an ecosystem? Students made posters and built 3-dimensional models of their proposed ideal ecosystems, and included a variety of existing and plausible-but-fictional organisms, described their system’s carrying capacity and how it maintains dynamic equilibrium, showed the relationship between producers and consumers, and highlighted symbiotic relationships with a habitat of their own design. 

One student was overheard in the ChangeMaker Lab during a work session saying, “This is my favorite science project of the year!” Overall, the classes really enjoyed the combination of applying science principles to a creative project that allowed them to literally construct their understanding of population dynamics.


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