A comprehensive hands-on inquiry lesson where students design, assemble, monitor, and analyze a multi-tiered bottle ecosystem to investigate biotic-abiotic interdependence, nutrient cycling, energy flow, and systems stability.
Pre-soak seeds for 2 hours for rapid 48-hour germination.
Ethical Animal Care & Bio-Safety Standards
Humane Oversight: Small invertebrates (snails, isopods) are living organisms that require respect. Never use vertebrates (e.g., feeder goldfish, bettas) in small 2-liter bottles as waste builds up too quickly and causes lethal toxicity. Instruct students to inspect water clarity daily. If foul odor, ammonia spikes, or severe distress occur, intervene immediately to aerate or release organisms.
Project the Ecobottle Explorers Slide Deck. Introduce the Biosphere 2 historical experiment and challenge students to conceptualize Earth as a closed system for matter.
• Student Action: Complete Part 1 of the Lab Worksheet (Blueprint & Chamber Predictions).
• Key Check: Ensure teams understand the function of each chamber and how the cotton wick acts as a xylem/capillary conduit.
Follow assembly protocol: 1) Build Aquatic Zone (gravel, conditioned water, elodea, snail); 2) Construct Decomposition Zone with wick; 3) Layer Terrestrial Zone with moist soil and seeds; 4) Secure joints with waterproof tape.
• Safety Note: Teacher cuts 2L bottles ahead of time or strictly monitors utility scissors.
• Baseline Data: Record initial water clarity, water level, seed count, and temperature before sealing.
PHASE 3
Longitudinal Monitoring & Logging (Days 3–13 • 10 min daily)
Daily Warm-up Routine
First 10 minutes of each class period: Students inspect bottles without opening the seal. Record quantitative growth (seedling height, leaf count) and qualitative signs (droplets on walls, snail activity, mold/fungi emergence).
Students graph longitudinal trends, analyze whether dynamic equilibrium was maintained, and write a formal CER argument. Humane deconstruction protocol: return snails and pillbugs to classroom vivarium or native habitat.
• Student Action: Complete Part 3 (Analysis) and Part 4 (CER Argumentation).
• Socratic Debrief: Facilitate whole-class discussion comparing systems that thrived vs. those that experienced collapse.
Daily 5-Point Health Inspection Checklist
1. Wall Drops Active water cycle
2. Water Tint Clear vs green/brown
3. Snail / Bug Active movement
4. Mold / Decay Normal decomposers
5. Plant Color Vibrant green
Ecobottle Builders Facilitation Guide Page 2 of 3
Facilitation & Troubleshooting
Diagnosis, Questioning & Assessment
Teacher Reference
Ecobottle Troubleshooting Matrix
Observed Symptom
Root Ecological Cause
Pedagogical Question & Corrective Action
Pea-soup green aquatic water
Uncontrolled algae bloom caused by excess light or nutrient runoff from soil above.
"What abiotic factor is fueling the algae?" Move bottle out of direct beam; shroud bottom chamber with paper for 2 days.
Heavy fuzzy white mold on soil
Stagnant moisture and high humidity combined with unsterilized decaying matter.
"Is mold biotic or abiotic? What role does it play?" Explain saprophytic fungi. If overwhelming, vent top for 30 minutes.
Aquatic snail remains at waterline
Low dissolved oxygen (hypoxia) in water; snail is breathing atmospheric air.
"Why might the water lack oxygen?" Check if Elodea has died or needs more light to produce O₂ through photosynthesis.
Seedlings yellow and spindly (etiolation)
Insufficient light intensity; plants are burning energy stretching toward photon source.
"How does light affect chloroplast activity?" Move closer to LED grow light or south-facing window.
Higher-Order Systems Thinking Prompts
Energy vs. Matter
"If we wrap the entire bottle in black foil, which cycles stop first and why? Could matter continue cycling without incoming energy?"
Equilibrium & Feedback
"What negative feedback loop occurs when the snail produces CO₂ and the aquatic plant consumes it? What would break that balance?"
Support & Scaffolding (IEP / ELL)
• Provide pictorial sentence starters for CER ("The evidence that matter recycled is...")
• Pair visual diagrams with color-coded cycle arrows (Blue = H₂O, Green = CO₂, Red = O₂).
• Use structured graphic organizers with pre-drawn bottle chambers.
Extension & Advanced Inquiry (Gifted)
• Introduce controlled experimental stressors: compare a standard bottle with one under 24h continuous light vs. dark.
• Quantify dissolved oxygen or pH using micro-test strips through a re-sealable silicone sampling port.
• Model human colonization challenges (Mars terraforming / Biosphere 2 failure analysis).
Tiny oxygen bubbles streaming from Elodea leaves; survival of snail/isopods without asphyxiation.
Nitrogen / Nutrients
(\(NO_3^-\), Organic Waste)
Decomposers and nitrifying bacteria break down animal fecal pellets and dead leaf biomass into inorganic nitrates (\(NO_3^-\)) absorbed by roots.
Disappearance of fallen leaves/debris; vigorous green plant growth without supplemental fertilizer.
2. Exemplar Response: Energy Flow vs. Matter Cycling 4 Pts
Model Student Response: "Energy obeys the laws of thermodynamics: it cannot be recycled. Solar energy enters as light, is transformed into chemical bonds by plants, powers cellular work, and is eventually lost from the bottle as diffuse thermal heat energy. Therefore, light must continually be supplied. In contrast, matter is conserved (Law of Conservation of Mass); atoms of C, H, O, and N are continuously rearranged into new molecules and cannot escape the sealed bottle."
KEY: PART 3 Investigation Variables & Hypothesis Rubric
6 Points Possible
Independent Variable (IV) Light condition (e.g., standard 12h photoperiod vs. constant darkness) OR bottle closure state (sealed baseline vs. unsealed).
Dependent Variables (DV) Seedling stem elongation (cm), aquatic water clarity (turbidity index), snail/isopod survival and locomotion rate, condensation rate.
Controlled Variables (CV) Ambient room temperature, volume of water (500 mL), mass of gravel/soil, species and count of organisms introduced at baseline.
"If a multi-chamber ecobottle is provided with 12 hours of indirect sunlight daily with a balanced ratio of 1 plant to 1 snail, then the ecosystem will maintain clear water and plant growth over 14 days without organism mortality, because photosynthesis by Elodea and terrestrial seedlings will generate sufficient oxygen and consume the carbon dioxide produced by the animals and decomposers."
KEY: PART 5 Exemplar CER Scientific Argument & Rubric
12 Points Total
Model Claim (3 Pts): "Our ecobottle successfully established and maintained a self-sustaining dynamic equilibrium over the 14-day observation period."
Model Evidence (5 Pts): "Over 14 days, the aquatic water remained clear with zero mortality of the snail, which grazed continuously. Terrestrial seedlings grew from seeds into a 6.2 cm dense canopy with 100% survival. Water continually cycled, evidenced by dense condensation beads every morning that precipitated back onto the soil, maintaining a stable reservoir level within 2 mm of baseline."
Model Reasoning (4 Pts): "This equilibrium occurred because the rate of oxygen production by the terrestrial grass and aquatic Elodea through photosynthesis matched or exceeded the oxygen demand of the snail, isopods, and microbial decomposers for cellular respiration. Concurrently, the decomposers recycled dead leaf tissue into bioavailable nitrates, ensuring a closed nutrient loop without toxic ammonia accumulation."
Note on Unbalanced/Collapsed Ecobottles: If a student's bottle failed (e.g. water turned cloudy brown, snail died, plants molded), students can still earn full marks on the CER if their Claim states that equilibrium was not achieved, their Evidence cites the specific failure metrics (e.g., cloudy water on Day 6, snail dormancy at surface), and their Reasoning correctly identifies the ecological breakdown (e.g. overpopulation depleting dissolved oxygen faster than photosynthesis could replenish it).
Ecobottle Lab Packet Total Score: Part 1 (15) + Part 2 (13) + Part 3 (6) + Part 4 (10) + Part 5 (12) = 56 Points Total
