There is a lot of life above the earth. But in most systems, there is more life BELOW the soil than above it.  A handful of soil has more organisms in it then there are people in the world. Soil biology is all of the fungus, animals, and bacteria, and how it is processed in the soil. When these bacteria, fungi, and animals die, the living organisms in the soil eat the dead, creating organic matter.  These reactions are dependent on the type of soil, and on the decisions that humans make. 

Soil biology is very important, as healthy soils can store carbon in the soil, as opposed to releasing it into the atmosphere. Soils that are not regularly tilled and are covered by plant life are generally healthier, and have more types of bacteria and animals, and more organic matter. These soils erode less, and have more nutrients available for plant food.

This lesson plan is appropriate for grades 4+. Some of the details and organism names may be better suited for older students.


Soil Biology

Lesson Objectives:

1) What types of organisms live in the soil?

2) What do soil organisms feed upon?

3) How do these organisms benefit humans?


Glossary of terms:

In current glossary:

  • Decompose (Decomposition)

  • Fungus (plural Fungi)

  • Microbes

  • Microbiologist

  • Organisms

Other glossary words:

  • Bacteria  -- Single-celled organisms that are microscopic ranging in shape from spheres, rods, to spirals.

  • Earthworms  --  Long, thin segmented animals that burl through the soil aerating and enriching it.

  • Mites  --  Eight-legged animals too small to see with the unaided eye that feed on smaller organisms and soil organic matter.

  • Nematodes  --  Tiny, non-segmented worm-like organisms that mostly live on other organisms or soil organic matter.

  • Protozoa  --  Single-celled organisms larger than bacteria that move in water films and feed on bacteria and soil organic matter.

  • Rotifers  --  Microscopic animals found in many freshwater environments and in moist soil that move by swimming or crawling.

  • Springtails  --  Six-legged animals that often have a tail-like structure folded beneath the body that can be used for jumping when the animal is threatened.


Activities or information:

1) Teaching with worms


2) Soil biological communities

  • What is Soil - NSTC (grades 4-6)  This site have multiple activities including general information, coloring, collecting soil bugs, seeing soil color and feeling soil texture, and making your own earthworm farm.
  • Soil Biological Communities - NSTC (grades 4-8)  This is an informational site that explains soil organisms and their interactions. It has mainly text and pictures.


3) Composting for better soil

  • Composting for A Better Soil - New York AITC (PDF) (grades 4-5)  This is a teacher’s guide for composting with all sorts of activities, including worksheets, matching, building a compost bin, evaluating compost for plant growth, a glossary, and other items.


4) What’s living in my soil


5) Microbial Diversity in the Soil

6) Soil biology movies


Test Questions:

1) Which organism has the largest number of species in the soil?  

  • Bacteria

​2) Name five organisms that live in soil?

  • Rotifers, earthworms, mites, protozoa, springtails, nematodes, bacteria.

3) What is decomposition?

4) How do humans benefit from soil organisms?