Earth's Day Craft Idea - build an eco-system in a jar

Just thought that this could be a great Earth's Day themed craft for kids.

Tropical rain forests are one of the most endangered ecosystems in the world. Educating kids the importance of preserving rain forest becomes easier if they understand what an ecosystem is.

Materials:

An empty glass jar with lid
Some Moss and Charcoal
Some Pebbles and Soil
A small and slow growing plant. Ensure the plant can fit into the glass jar.
Colorful seashells (optional)

Method:

Soak moss in some water to make it damp. Put all pebbles into glass jar. Add the charcoal followed by some damped moss. Add on the soil and small plant. Put the final layer of damped moss on top of soil. Do not cover the plant with the moss. Ensure the moss and soil is compact. Decorate with seashells if you want.
Sprinkle some water before cover with the jar’s lid. Put glass jar in a sunny spot.

To care for this miniature ecosystem in a jar, sprinkle water into the jar if it looks dry. Rotate the jar every couple of days to ensure every side gets even amount of sunlight.