• Base of a 2L pop bottle
• Bottom-half of a second 2L pop bottle
• Pipe cleaners
• Beans or small plants
• Potting soil
• Rocks or broken clay pieces
• One-hole punch
• Water

1. Cut the base of an empty 2 L pop bottle off.
2. Cut the bottom half of another 2 L pop bottle off.
3. Use the base as a lid for the bottom half. Line up the base and the lid and punch two holes in each, an equal distance apart.
4. Fill up bottom of your base with rocks or broken clay pieces.
5. Fill container up to 3/4 full with potting soil.
6. Dig a small hole in soil and place bean or plant at bottom. Cover over with soil and water.
7. Place lid on top and line up punched out holes. Weave pipe cleaner through and tie outside of container.

Plants do not have to go out and hunt for food; they make their own food. The leaves of most plants act like mini food factories where they make food called carbohydrates, or sugars, for the rest of the plant. To make this food, leaves need three essential ingredients: water from the soil, carbon dioxide from the air and energy from the sunlight.

A terrarium takes advantage the process of "transpiration". Transpiration occurs when the roots of plants absorb moisture from the soil. The water passes through a plant's stem, through the branches to the leaves and then evaporates into the air from the surface of the leaves. In the terrarium, the water vapour condenses on the lid and water droplets "rain" down on the plants.

Keep the terrarium near a window, but not in direct sunlight. Rotate the terrarium regularly so that plants don’t grow in one direction. You should always be able to see some water droplets on the lid. If there are no water droplets, add some water to the terrarium. If there seems to be too much water in the terrarium, take the lid off for a few hours.

A terrarium behaves like a small ecosystem, which is a community of living organisms and resources. The main living organisms in a terrarium are the plants and the micro-organisms in the soil. The resources of the terrarium are sunlight, water and soil.

Like a real ecosystem, the terrarium is completely sustainable. That means that everything in the ecosystem works together to produce what is needed for all the living organisms in it to survive.

An ecosystem, like a terrarium, could be sealed up and still survive because everything in the ecosystem works together. However, ecosystems require specific conditions to function properly and small changes can derail an entire system! This is why human interference such as pollution, deforestation and poaching can harm more than just one species.