Decomposers, the final links in food chains, use dead plants and animals as food, breaking them down into smaller particles. Among the decomposers are fungi, which include the familiar molds and mushrooms. Other decomposer -- called bacteria -- are so small that a mere teaspoon of soil could contain billions of them.
Composting happens when humans promote this natural process of decomposition and nutrient cycling by creating an environment in which particular decomposers thrive. As the decomposers use the organic matter for energy and maintenance, they break it down into simpler molecules that can be used again as nutrients for plants, and the cycle begins all over again. This process also give off heat, which in turn speeds up decomposition. While microorganisms accomplish most of the chemical decomposition in a compost pile, small invertebrates such as sowbugs and earthworms are responsible for much of the physical breakdown of materials.
Although your students can't actually see many of the decomposers, they can explore their behavior up close. Whether you plan to build an outdoor compost pile or not, you can lay the groundwork with some exploratory activities. Consider the following: