Classroom Snapshot
A tagged bar-tailed godwit leaves Alaska at 560 g, flies across the Pacific for about ten days without landing, eating, or drinking, and arrives in New Zealand at 300 g. Where did 260 g of bird go? Students commit to a first idea, then build the evidence step by step: a balanced equation, an energy ledger, tracer evidence, and a mass ledger. They finish with a claim, evidence, and reasoning explanation and apply the same idea to germinating seeds in a sealed jar.
What Students Learn
Students use a balanced equation to show that cellular respiration rearranges the atoms of glucose and oxygen into carbon dioxide and water, with the same 6 carbon, 12 hydrogen, and 18 oxygen atoms on both sides.
Students explain that the energy comes from bond changes: forming the bonds in CO₂ and H₂O releases more energy than it took to break the bonds in glucose and O₂. About a third of that energy is captured in ATP and the rest is released as heat. No mass is turned into energy.
Students trace the atoms out of the body and show that mass in equals mass out, so most of the fuel’s mass leaves as exhaled carbon dioxide and the rest leaves as water.
Lesson Flow
- The flight. Students run the flight on a map, see that the bird lands 260 g lighter with nothing taken in, and choose a first idea for where the mass went. Any choice is accepted; the lesson brings it back at the end.
- Balance the reaction. A short reading introduces cellular respiration, mitochondria, and what goes in and out. A worked example balances carbon and explains coefficients versus subscripts; students then balance hydrogen and oxygen with +/− buttons and a live atom count.
- Follow the energy. Two bond rules come first: breaking a bond costs energy, and forming a bond releases energy. Students run an energy ledger for one mole of glucose (about 12,400 kJ to break the reactant bonds and about 15,100 kJ released forming the product bonds, for a net of about 2,700 kJ), then split the released energy into ATP and heat.
- Follow the atoms. Tracer evidence and a worked example show carbon’s route from a muscle cell to the lungs. Students complete a mass ledger (180 g glucose + 192 g O₂ = 372 g in; 264 g CO₂ + 108 g H₂O = 372 g out), then step through the whole flight day by day. By Day 10 the model shows 260 g of fuel and 277 g of O₂ in, and 381 g of CO₂ and 156 g of water out.
- Explain the flight. Students choose a claim, the two strongest pieces of evidence, and the reasoning that links them, transfer the idea to germinating bean seeds in a dark, sealed jar, and see their Act 1 idea again alongside the evidence.
What's Included
- A free, browser-based interactive lesson (no student accounts, logins, or data collection)
- This teacher planning guide with learning goals, lesson flow, and classroom-use notes
- Grade band, timing, and activity-type details for quick planning
Best Used For
Introducing or reviewing cellular respiration in high school biology, connecting biology to conservation of mass from chemistry, or following a photosynthesis lesson with its reverse. Works for grades 7–12 (aimed at grades 9–10) as a projected class activity or independent practice.
How the Lesson Teaches Before It Assesses
Every checked task comes after an explanation, and the equation and atom-tracking tasks each start with a worked example. Wrong answers get specific coaching that becomes more direct after two misses. Every interaction is a button or a typed number; no dragging is required.
Common Misconceptions It Targets
- The lost mass was turned into energy.
- Burning fuel destroys matter, so the mass was “used up.”
- Most of the mass left as droppings.
- Energy is stored inside a bond and bursts out when the bond breaks.
- Only animals carry out cellular respiration; plants only photosynthesize.
Teacher Notes
The bird’s masses are illustrative for one bird, though real godwits lose a similar share of their body mass. Real godwits burn mostly stored fat (plus some protein); the lesson follows glucose as the simplest fuel and says so on screen. The whole-flight model treats all lost mass as fuel burned with glucose ratios, which is why the Day 10 totals scale up from the one-glucose ledger.
Mass calculations use whole-number atomic masses (C 12, H 1, O 16), and Act 4 has a pop-open calculator. The bond-energy values are rounded averages, so the net figure is an estimate; the measured value for glucose is slightly higher. The three stages (glycolysis, Krebs cycle, electron transport chain) appear only in an optional “zoom in” panel and are never checked. The lesson ends with a reminder to take a screenshot of the final summary if you want a record.
Accessibility
The flight map, molecules, and images have screen-reader descriptions, and correct and incorrect results are marked with symbols as well as color. Focus moves to each new scene and to feedback, results are announced as they appear, and students can go back or resume where they left off.
Privacy and Classroom Use
The interactive lesson runs in the browser without student accounts, names, or emails. Teachers can project it, assign it directly, or pair it with optional print materials. The site uses cookieless usage analytics; see our Privacy page for analytics and browser storage details.