2026–27 · Backup lesson · Spring 2027
Map Gas Exchange in a Garden System
Adult extension of: Plants and Animals Exchange Gases
Unscheduled alternative · available resource
Build separate photosynthesis and respiration pathways to explain how plants, animals, and air are connected. Use the model to challenge the idea that plants only take in carbon dioxide or that a few indoor plants replace ventilation.
Curriculum skill focus: Systems thinking, gas exchange, plant-animal relationships, sequencing
01 · Learning
Objectives
- Distinguish oxygen and carbon dioxide in a simple labeled model.
- Represent respiration in both plants and animals.
- Explain why the model does not establish air quality or ventilation needs.
02 · Preparation
Materials
Large plant, animal, and air cards; labeled oxygen and carbon-dioxide cards; different-texture or labeled arrows; light and sugar cards; leaf stomata photograph; blank model sheet; optional realistic garden-system photo.
03 · Practice
Adult project
- 1
Choose a familiar garden scene and identify the plants, animals, and surrounding air. Explain that the gases cannot be identified by ordinary sight, and choose card handling, directing, spoken modeling, or observation roles.
- 2
Build an animal-respiration pathway showing oxygen used and carbon dioxide released as cells obtain usable energy from food. Keep normal breathing optional and do not use a breath-holding or forced deep-breathing exercise.
- 3
Build a separate plant-photosynthesis pathway in suitable light, with carbon dioxide and water used to make sugars and oxygen released. Label the pathway photosynthesis instead of giving the plant a single permanent gas-direction arrow.
- 4
Add plant respiration alongside it: plant cells also use oxygen and release carbon dioxide as they release usable energy from sugars. Show respiration in both light and darkness and explain that the net balance varies with conditions.
- 5
Connect both organisms to the shared air pool, not to an exclusive one-plant-one-animal exchange. Examine a stomata image and discuss it as a gas-exchange structure while noting that the image alone does not show gases moving.
- 6
Complete the model with one statement that it supports and one claim it cannot support. Apply the limit to indoor spaces: care for plants for their appropriate uses while following normal ventilation guidance rather than treating the model as an air-quality measurement.
Evidence & interpretation
What the investigation shows
Plants and animals carry out cellular respiration; photosynthetic plant tissues additionally use carbon dioxide and release oxygen in sufficient light. Net exchange depends on conditions and rates, and a simple gas-arrow model cannot quantify indoor air quality or justify replacing ventilation with houseplants.
Practical connection
Why this work matters
Systems thinking connects garden ecology with realistic expectations about plants in indoor and outdoor spaces.
Participation by choice
Individual access options
- Use labeled or textured arrows so the model does not depend on color recognition alone.
- Choose a two-pathway comparison, a fuller system map, or direct a partner’s card placement through speech, gaze, or AAC.
- Skip all body-awareness prompts, use only external images, and pause or leave the modeling activity whenever preferred.
Review & transfer
Reflect on the work
- Why does a plant need more than one gas-exchange pathway in the model?
- What real measurement would be needed before making a claim about indoor air quality?