BACKGROUND:

An ecosystem is a community of plants and animals, which consists of many individuals and populations.  Ecosystems can be any size from a small puddle containing algae and protozoa to the Amazonian rain forest.  An ecosystem is made of two components:   the physical environment and the biological community.   

In soil,  animals, insects, and microorganisms help to maintain a cycle that is very important to the survival of life, the nutrient cycle.  Animals such as rabbits, gophers, and badgers use the soil for shelter and food.  When you want to make soil with added nutrients you add compost, which is broken down organic matter.  Many organisms can thrive in a nutrient rich environment.

These animals burrow into the ground and cause large pieces of soil to be loosened.  Once the larger pieces of soil are loosened, it is easier for insects and worms to travel and move about in the soil.  The moving action of these insects and worms causes the smaller particles of soil to be loosened and mixed with air and water that has penetrated the soil.  The air and water can easily enter the soil once it is loosened.  The air and water mix with nutrients and creep down into the soil and provide the necessary growing conditions for plant roots.  These roots absorb the air, water, and nutrients, and provide food for humans and animals.  Compost and the organisms that they promote make healthy soil for plants.

Soil  microorganisms such as bacteria break down organic materials and rock and release nutrients.  Without this breakdown, the soil would not have the nutrients for use by plants.  These organisms that break down organic material are called decomposers and are responsible for the fertility of the soil. Although your students  may not see all this occurring, they can start to understand the importance of soil. 

PROCEDURE:

1. Prior to this exercise, go outside and find a place that might look interesting for students to investigate.  An area where there is overgrown vegetation would be ideal or under a tree.  Freshly mowed grass would not be a good area, nor asphalt. If you have trouble finding an area, you could set an area where students may play and assign as a homework assignment. 
   
2. Read "Compost Break Dance" and go over the organisms in organic matter that can help enrich soil.  Remember soil is "rocks plus organic matter."
     
3. You may want the students to work in groups of 4.  They should measure an area about 1 meter square.  They can put sticks at each corner so they try to keep inside the square.  This helps to compare equal areas. 
     
4. Instruct the students to describe on the worksheet the soil, animals, and vegetation that are present.  Record what you see.
     
5. After students record their information, you may want to discuss if there is an ecosystem in the school yard.  Are there plants and animals that are dependant on each other, or it ecosystem not well defined and maintained by the school gardener.