Science activity
Ecosystem in a Jar
Build a tiny world inside a jar! Add soil, plants, and water to make a mini garden that takes care of itself. Watch what happens to the water inside — it makes rain!
Materials and setup
- large clear jar with lid
- pebbles
- potting soil
- small plants or moss
- water spray bottle
- activated charcoal (optional)
- small sticks and rocks
How this changes by age
Pre-K (ages 3–4)
Build a tiny world inside a jar! Add soil, plants, and water to make a mini garden that takes care of itself. Watch what happens to the water inside — it makes rain!
Steps
- Find a large clear jar with a lid (a big pickle jar works well).
- Add a layer of small pebbles at the bottom for drainage.
- Add a thick layer of soil on top of the pebbles.
- Plant 2-3 small plants or moss clumps from outside. Water lightly.
- Close the lid tight and place in a spot with indirect sunlight. Watch for water drops on the glass — it is raining inside your jar!
- Tell a grown-up one thing that surprised you.
Learning objectives
- Build a simple terrarium representing a mini ecosystem
- Observe the water cycle happening inside a closed container
- Understand that plants need soil, water, and light to survive
Kindergarten (ages 5–6)
Build a terrarium ecosystem and observe it over time. Add different types of plants and small organisms. Track changes daily and learn about the water cycle happening inside.
Steps
- Gather materials: large clear jar, pebbles, activated charcoal (optional — helps prevent mold), potting soil, moss, small plants, and water.
- Layer in order: pebbles (1 inch), charcoal sprinkle, soil (2-3 inches).
- Plant small ferns, moss, or tiny houseplant cuttings. Add a few small sticks or rocks for decoration.
- Mist lightly with water (not too much!). Seal the jar.
- Observe daily for 2 weeks: draw what you see. Where do water drops form? Are the plants growing? Do you see any tiny bugs?
- Explain the water cycle in your jar: water evaporates from soil, rises as vapor, condenses on the glass, and drips back down like rain.
- Tell a grown-up one thing that surprised you.
Learning objectives
- Build a functioning closed terrarium ecosystem
- Observe and describe the water cycle inside a sealed environment
- Track changes in a mini ecosystem over a two-week period
Early elementary (ages 6–8)
Create and study a closed ecosystem: build a terrarium with multiple plant species, observe ecological interactions, compare open vs closed systems, and learn about nutrient cycling.
Steps
- Research terrarium ecosystems: a closed terrarium is a model of Earth's water and nutrient cycles. Plants produce oxygen and absorb CO2. Bacteria decompose dead material and return nutrients to the soil.
- Build two terrariums: one CLOSED (sealed jar) and one OPEN (no lid). Use the same plants, soil, and water amount in each.
- Observe both daily for 3 weeks. Track: condensation level, plant growth, soil moisture, any mold or decay, and overall plant health. Record in a data table.
- Compare: does the closed or open terrarium do better? Why? (Closed ones retain moisture; open ones may dry out or have different gas exchange.)
- Diagram the cycles happening inside: water cycle (evaporation, condensation, precipitation), oxygen-carbon dioxide cycle (photosynthesis and respiration), and nutrient cycle (decomposition returns nutrients to soil).
- Write a report explaining how your terrarium models Earth's ecosystems. What are the similarities? What important things are missing (animals, weather, seasons)?
- In one sentence, tell a parent or sibling what surprised you today.
Learning objectives
- Compare open and closed terrarium ecosystems through controlled observation
- Diagram the water cycle, gas exchange, and nutrient cycling within an ecosystem
- Analyze how a terrarium models Earth's larger ecological systems
Upper elementary (ages 8–10)
Design and conduct a comprehensive ecosystem study: build multiple terrariums testing different variables, monitor ecosystem health indicators, research Biosphere 2, and analyze what makes ecosystems sustainable.
Steps
- Build 4 terrariums with different conditions: (1) Standard closed (control), (2) Closed with added small organisms like isopods or springtails, (3) Closed with only moss (low diversity), (4) Closed with high plant diversity (5+ species).
- Monitor all four weekly for 4+ weeks. Track quantitative data: number of water drops visible, plant height changes, leaf count, color health rating (1-5), and any observable organisms.
- Research Biosphere 2: the ambitious 1990s experiment to create a self-sustaining human habitat. What went wrong? (CO2 buildup, oxygen depletion, species die-offs.) What does this teach about ecosystem complexity?
- Analyze your results: which terrarium is healthiest? Does biodiversity matter? Do decomposers make a difference? Create comparison graphs.
- Research ecosystem services: what do natural ecosystems provide that humans need? (Clean air, water filtration, pollination, climate regulation.) How does losing biodiversity threaten these services?
- Write a comprehensive ecosystem paper: present your experimental design, data with graphs, analysis of what makes ecosystems sustainable, Biosphere 2 research, and a discussion of why biodiversity matters for human survival.
- In one sentence, tell a parent or sibling what surprised you today.
Learning objectives
- Design multi-variable ecosystem experiments and monitor health indicators
- Analyze how biodiversity and decomposers affect ecosystem sustainability
- Evaluate real-world ecosystem engineering attempts and explain why complexity matters
Safety and evidence note
Read the full activity before beginning. An adult should supervise tools, heat, food, outdoor work, movement, and experiments as appropriate. Completion records that the activity was done; the child’s explanation, work sample, photo, or demonstration is stronger evidence of learning than a completion check alone.
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