Travel underground for an up-close look at the ants, amoebas, and bacteria that maintain healthy soil. Glimpse this microscopic world and learn about the symbiotic relationship between fungi and tree roots.

Guiding Questions

  • What role do decomposers like fungi and bacteria play in an ecosystem, and why are they important?
  • Would you describe the relationship between the tree's roots and the underground fungus as competition, parasitism, or mutualism? Why?

Connections to Standards

Next Generation Science Standards Disciplinary Core Ideas

  • LS1.C: Organization for Matter and Energy Flow in Organisms
    • (9-12) As matter and energy flow through different organizational levels of living systems, chemical elements are recombined in different ways to form different products.  As a result of these chemical reactions, energy is transferred from one system of interacting molecules to another.
  • LS2.A: Interdependent Relationships in Ecosystems
    • (5) Some organisms, such as fungi and bacteria, break down dead organisms (both plants or plants parts and animals) and therefore operate as “decomposers.” Decomposition eventually restores (recycles) some materials back to the soil.
    • (6-8) Organisms, and populations of organisms, are dependent on their environmental interactions both with other living things and with nonliving factors.  Mutually beneficial interactions may become so interdependent that each organism requires the other for survival.
  • LS2.B: Cycles of Matter and Energy Transfer in Ecosystems
    • (5) Matter cycles between the air and soil and among plants, animals, and microbes as these organisms live and die. Organisms obtain gases, and water, from the environment, and release waste matter (gas, liquid, or solid) back into the environment.
    • (6-8) Food webs are models that demonstrate how matter and energy is transferred between producers, consumers, and decomposers as the three groups interact within an ecosystem.  Transfers of matter into and out of the physical environment occur at every level.  Decomposers recycle nutrients from dead plant or animal matter back into the soil in terrestrial environments or to the water in aquatic environments.  The atoms that make up the organisms in an ecosystem are cycled repeatedly between the living and nonliving parts of the ecosystem.
    • (9-12) The chemical elements that make up the molecules of organisms pass through food webs and into and out of the atmosphere and soil, and they are combined and recombined in different ways. At each link in an ecosystem, matter and energy are conserved.
  • ESS2.A: Earth Materials and Systems
    • ​(4) Water, ice, wind, living organisms, and gravity break rocks, soils, and sediments into smaller particles and move them around.

California's Environmental Principles and Concepts

  • Principle III: Natural systems proceed through cycles that humans depend upon, benefit from, and can alter.
    • Concept a: Students need to know that natural systems proceed through cycles and processes that are required for their functioning.


Vocabulary for Students

  • amoeba: single-celled organism that has no definite shape 
  • decomposer: an organism, usually a bacterium or fungus, that breaks down the cells of dead plants and animals into simpler substances
  • eukaryote: an organism whose cells contain nuclei
  • fungi: eukaryotes that have cell walls, feed by absorbing their food, and use spores to reproduce
  • hyphae: the branching, threadlike tubes that make up the bodies of multicellular fungi
  • mutualism: a close relationship between organisms of two species in which both organisms benefit
  • nematodes: round-bodied unsegmented worms
  • symbiosis: a close relationship between two or more organisms of different species, which is often--but not always--beneficial for one or both organisms

How Have Teachers Used this Video Clip?

To Teachers, From Teachers

"I would like to show our 4th grade students the Soil Beneath Our Feet video, as part of our lesson on decomposers--to better provide visual representation of how microorganisms and fungi go about their business." -Informal Science Educator from Sonoma, CA

"The videos are visually engaging, helping to illustrate ideas that are fairly abstract for intermediate grade levels: photosynthesis and transpiration for example, as well as the idea that ecosystems range from the vast spaces of a kelp forest to the tiny world of microbes at a tree's base in the soil." -Grades 1-6 Science Specialist from Fremont, CA

"I would love to use some of the videos and guiding questions as a way to provide connections to real-world phenomenon." -High School Life and Physical Science Student Teacher from Berkeley, CA

Have an idea you'd like us to post on this page? Email us.

Visualizations based on aggregated data provide the unique opportunity to engage your students in various Science Practices highlighted in the Next Generation Science Standards, including asking questions, analyzing and interpreting data, and constructing explanations. As an example, Academy educators developed sample activities such as this one and this one.

Related Long-term Project: Macroinvertebrate Manor (grades 3-5)


Construct a home for macroinvertebrates right outside your classroom! Third graders observe this created habitat, discovering which organisms can survive well and how they change when their environment changes. Fifth graders develop a model to describe invertebrate habitats and the movement of matter among the plants, animals, decomposers and the environment. This project is designed to span a month or longer.

Related Outdoor Activities: Living Schoolyard Guide (grades preK-12)

garden sign

As a contributor to this guide featuring over 40 activities, the Academy encourages schools to take their students outside throughout the year. Celebrate your school grounds and use them for hands-on learning, place- based inquiry, recreation, environmental stewardship, and community-building.

Related Investigation: Rate of Decomposition (grades 3-5)


In this two-part inquiry-based activity, students will practice using the scientific method while learning about decomposition, exploring how some types of garbage will decompose while others will not. Students will design their own experiment to test different variables affecting the rate of decomposition.

Recommended Resources

Diving into Soil
How did our digital artists create the organisms featured in this show? There’s a laundry list: ants, moss mites, nematodes, amoebae, bacteria and fungi entwined with tree roots.

Friendly Fungus
This video explains how fungi are essential in providing moisture to soil and plants, and play a huge role in decomposition.

Ecosystems and Ecological Interactions
Read more about mutualism, commensalism, parasitism, and competition, and watch this tutorial to better understand the importance of biodiversity.

Microbes Beneath the Surface
This science news article summarizes a study focusing on the bacteria living within grassland soils, and includes a link to the scientific paper itself!

Carnivorous Mushrooms and the Human Immune Systems
Scientists hope that by learning about the proteins used by fungi, we can create new drugs for doctors to use with people who suffer from auto-immune diseases. Read this article to get the scoop.

Fat Fighting Fungi
This article describes how a particular fungus could prove useful as a treatment for obesity.

Data Sources

Forest Data
Peter A. Steel Angelo, Coastal Range Reserve, University of California
Raptor View Research Institute, Missoula, Montana
Scientists at the H.J. Andrews Experimental Forest
​Sherri Johnson

Animated Species Reference
Collections of the California Academy of Sciences
Christina Piotrowski, Collection Manager, Invertebrate Zoology & Geology
Debra Trock, Senior Collections Manager, Botany

Nematode Model
Dr. Christian Drove and Dr. Paul Sternberg
Virtualworm Project

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