Matter Trails in a Winter Atrium

A Warm Place in a Snowy Town

Snow covers the streets around Northbridge Town Hall. Inside, a glass-roofed atrium stays warm. Small fig trees grow in large soil beds. Staff water the beds, and daylight enters through the roof. A screened observation box beside one tree holds land snails. Staff give the snails fresh fig leaves and water. Visitors can compare the leaves before and after feeding.

The town's science club is making a model of this small ecosystem. Its information cards explain that plants use matter from air and water to make food. Roots also take in water and small amounts of nutrients from soil. Animals use food matter to grow and to keep their bodies working. Animals also release matter in waste and into the air. Fungi and bacteria are decomposers. They use dead material and waste as food, and they release matter into the surrounding soil and air. Sunlight supplies energy, but it is not matter.

Staff investigated fallen leaves in the soil beds. They prepared four mesh bags, each holding 20 grams of dry fig leaves. The mesh let air, water, fungi, and bacteria reach the leaves but kept snails out. All bags used the same mesh and similar leaves. Staff placed them in the same bed and gave them the same amount of water. They changed only how long each bag stayed there: zero, two, four, or six weeks. An adult removed and dried the remaining leaf pieces from each bag, then measured their mass.

During the investigation, staff saw fungal threads spreading over some leaf pieces. In the separate snail box, they saw bite marks on fresh leaves and collected snail waste. The graph records only the mass of dry leaf pieces remaining in the mesh bags. It does not include the mass of fungi, bacteria, soil, water, or air. The club must decide how to represent these observations with arrows. Each matter arrow will point from a source to a receiver and name the material being moved.