Self Sustaining Ecosystem in a Jar
Build a sealed terrarium ecosystem with soil, plants, and moisture. Watch the water cycle, photosynthesis, and decomposition happen in a closed system for weeks.
What You'll Need
- 1Large glass jar with sealable lid
- 2Small pebbles
- 3Activated charcoal (pet store)
- 4Potting soil
- 52-3 small humidity-loving plants (moss, ferns)
- 6Spray bottle with water
What You'll Need
A large glass jar with a sealable lid
Small pebbles for drainage
Activated charcoal (available at pet stores)
Potting soil
2-3 small plants: moss, ferns, or small tropical plants
A spray bottle with water
How to Play
Layer pebbles (1 inch), charcoal (thin layer), and potting soil (2-3 inches) in the jar.
Plant 2-3 small humidity-loving plants. Press roots into soil.
Spray until moist but not soaked. Seal the jar.
Place in indirect sunlight.
Watch for condensation within days — the water cycle in miniature.
Observe weekly: "Are the plants growing? Where does the water collect? What changes?"
"This jar is a tiny Earth — sealed, self-sustaining, recycling everything."
The Science Behind It
A sealed terrarium is a closed ecosystem. Plants photosynthesize (using CO2 and light to make oxygen and sugar). Water evaporates, condenses on the glass, and "rains" back down. Dead material decomposes and feeds the soil. Everything recycles. It's the same system that sustains life on Earth, just miniaturized. Some terrariums have survived for decades without being opened.
Tips
Choose plants that love humidity and don't grow too fast. Moss is ideal.
Don't overwater. Too much water causes mold. The soil should be damp, not soggy.
Indirect sunlight is key. Direct sun creates a greenhouse effect that can cook the plants.
If condensation blocks your view, the jar is too wet. Open briefly to let some moisture escape.
Start a weekly observation log: draw the jar, note changes, measure plant growth. This is longitudinal scientific observation.
The terrarium can live for months or even years if balanced correctly.
Frequently Asked Questions
How long does this activity take?
This activity takes about 30 min, with 10 min of preparation time beforehand.
What materials do I need?
You'll need: large glass jar with sealable lid, small pebbles, activated charcoal (pet store), potting soil, 2-3 small humidity-loving plants (moss, ferns), and 1 more item.
What age is this activity for?
This activity is designed for 8-12 years. You can adapt it for younger or older children by adjusting the complexity.
Can this be done indoors?
This activity is designed for indoor play, making it perfect for rainy days or when you're staying inside.
How difficult is this activity?
This activity has a moderate difficulty level. It may require some preparation or guidance, but is manageable for most families.
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