This lesson delivers the strand's summative assessment, Build an Ecosystem. Begin by reviewing the big ideas from the deck: producers make food from the Sun's energy; consumers eat other living things; decomposers return nutrients to the soil; food chains and webs show how energy flows; and arrows point towards the eater.
Model the expectations, not the answer: show a quick sketch of an unrelated ecosystem (e.g. a rock pool) and think aloud about including at least one producer, two consumers and a decomposer, drawing arrows the right way, and being ready to explain the relationships. Then remove your model so students design their own.
Brief, light-touch only (this is assessment): clarify the task parts and check every student understands what "producer", "consumer" and "decomposer" mean and how to draw the arrows. Confirm students know they are working individually and where to find support (word wall, sorting cards).
Students complete the Build an Ecosystem task individually: Part A (draw and label a tree-based ecosystem with two food chains), Part B (name each living thing's role in a table), Part C (explain a food chain's energy flow and the decomposer's job), and Part D (explain the flow-on effects of removing one living thing).
Finish with a short gallery walk: students view a few peers' ecosystems and answer one "what if…" question (e.g. "What if there were no producers?"), consolidating the interdependence idea and giving a natural close to the strand.