The Sealed Garden: How Does Life Sustain Itself Without Anything New?
Shared by A STEM Educator
Students will construct an explanation (NGSS MS-LS1-6, MS-LS1-7) for how photosynthesis and cellular respiration together cycle matter (carbon, oxygen, water) and transform energy within a closed system, using evidence from the sealed bottle garden phenomenon and molecular-level models.
Lesson Overview
Students investigate David Latimer's sealed bottle garden — alive since 1960 with no new air, water, or nutrients — to uncover how photosynthesis and cellular respiration cycle matter and energy in a closed system. Students build toward explaining how living systems recycle atoms while continuously transforming energy.
Materials
- David Latimer bottle garden image (provided in lesson)
- Clear 2-liter plastic bottles with lids (1 per group)
- Small aquatic plants (Elodea) or fast-growing seedlings
- Soil, water, gravel
- Bromothymol blue (BTB) indicator solution
- Straws for breathing into BTB solution
- Bright lamp or sunny windowsill
- Aluminum foil (to block light for control)
- Stopwatch or timer
- Student investigation handouts
- Colored pencils (green, blue, red, yellow)
- Whiteboard markers for class modeling
Scaffolded Task Progression
Look at the sealed bottle garden image. In the table below, list what you think the plant NEEDS (inputs) and what you think the plant PRODUCES (outputs) just to stay alive. Use what you already know about plants.
| What the Plant NEEDS (Inputs) | Where it comes from in a SEALED bottle? | What the Plant PRODUCES (Outputs) |
|---|---|---|
After filling in the table: Circle any input where you wrote 'I don't know' for the source. These are your mystery questions for today.
A. Using colored pencils, color-code the molecules: CO₂ = red, H₂O = blue, O₂ = green, glucose = yellow. Color each molecule in BOTH equations.B. What do you notice about the products of one reaction compared to the reactants of the other?C. A student says: 'The plant makes oxygen during photosynthesis, but then uses it all up during respiration — so what's the point?' Write a 2-sentence response that agrees OR disagrees using evidence from the equations. [ Interactive graph / diagram — available in the full lesson ]
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