Safety and evidence boundary
This week uses atom-tracing models, fictional reaction sets, and supplied ecosystem data. No specimen collection, chemical reaction, or biological culture is required.
Explicit science instruction
At ecosystem scale, carbon moves through organisms and nonliving reservoirs. Photosynthetic organisms fix CO₂ into organic matter. Consumers obtain carbon by feeding. Cellular respiration can return carbon to CO₂. Waste and dead biomass move carbon into detrital pathways, where decomposers transform material and also respire.
Some carbon remains stored for longer periods in soils, sediments, oceans, wood, or geological reservoirs. The rate of transfer among reservoirs can vary from minutes to millions of years. A useful carbon-cycle model therefore includes both reservoir size and flux, the rate of movement between reservoirs.
Energy does not cycle in the same way. Solar energy enters ecosystems, chemical energy is transferred through organisms, and energy is progressively dispersed as heat. Continued ecosystem function depends on ongoing energy input.
Vocabulary: reservoir; flux; producer; consumer; decomposer; detritus; respiration; sequestration; timescale.
Worked example with reasoning
A fictional meadow contains 500 carbon units in plant biomass. Herbivores consume 40 units during a period; 15 become herbivore biomass, 20 are released through respiration and other outputs, and 5 enter waste/detrital pools. The accounting reminds us that “consumed” carbon is redistributed among reservoirs rather than disappearing.
Guided question
Why is a carbon-cycle diagram incomplete if it includes arrows for feeding but no arrows for respiration or decomposition?
Independent work
- Build a six-reservoir carbon model.
- Label at least eight fluxes.
- Choose one flux and identify the biological process responsible.
- Add one long-term reservoir.
- Draw energy flow separately and explain why the arrows do not form the same kind of closed cycle.
Misconception check
Decomposers do not “recycle energy” back to producers. They recycle matter through chemical transformations, while energy is transferred and ultimately dispersed as heat.
Formative understanding check
What is the difference between a carbon reservoir and a carbon flux?
Show the worked response
A reservoir is a quantity of carbon stored in a component of the system; a flux is the rate of carbon transfer between reservoirs.
Open-book formative practice only; not an official mastery attempt or grade.
Mentor evidence conference
Ask Archaemenes to inspect your atom or system model for a missing reservoir, an impossible disappearance of matter, or confusion between matter cycling and energy flow. Revise your own work after the conference.
Open Archaemenes for this lessonTeacher guidance
Foundation: use labeled reservoir cards and arrows. Core: distinguish reservoir from flux and matter from energy. Extended: compare reservoir size and turnover time and discuss why a large reservoir can have a small annual flux.
Preserve learning evidence
Keep the atom accounting, system model, correction notes, and explanation from this lesson in the corresponding Week 11 evidence field.
Return to thursday Evidence Workspace