Yikes, it’s alive!
Introduction
There is a lot of life on earth. But did you know that in many places, there is more life BELOW the soil than above it? A handful of soil contains more organisms than there are people in the world.
Most soil organisms are microscopic; that is, we can only see them with the help of a microscope. Soil microorganisms include bacteria, fungi, protozoa, nematodes, rotifers, tardigrades (water bears) and mites. We can also see larger soil organisms with the naked eye: macroscopic organisms living in the soil include earthworms, springtails, millipedes, spiders, ants, slugs, and moles.
These organisms are linked together in an intricate food web, just like communities above ground. At the bottom of the soil food web is organic matter – the dead remnants of plants, animals, and microbes – which decomposers (bacteria, fungi, earthworms) happily consume, breaking the organic matter down into simpler forms and releasing nutrients. Predators (nematodes, protozoa) feed on decomposers.
Healthy soil has a diverse community of organisms. This community supports life above ground. Decomposition breaks down waste, cleans the environment, stores carbon in soil, and provides nutrients for new life. Soil organisms living near plant roots, a zone called the rhizosphere, provide nutrients to the plant and can help protect them from disease or stress. Soil organisms produce substances that act as gels and glues that help give soil structure and larger organisms moving through soil, like earthworms, help aerate the soil. We can keep the soil and its organisms healthy by growing plants, reducing disturbances like tilling or digging, and keeping soil free of pollutants.
Learning Objectives:
- Identify some of the microscopic and macroscopic organisms that live in soils.
- Explain the beneficial functions of soil organisms that support life on this planet.
NGSS Connections:
- LS2.B: Cycles of Matter and Energy Transfer in Ecosystems
- ESS2.E: Biogeology
Glossary:
- Fungus
- Microbes
Click here for a Powerpoint (Note: The revised slide deck will be linked here.)
Discussion Questions:
1. What types of organisms live in the soil?
- Soil contains both microscopic (seen with the help of a microscope) and macroscopic (seen with the naked eye) organisms.
- Examples: bacteria, fungi, protozoa, rotifers, nematodes, mites, springtails, earthworms, millipedes, spiders, ants, slugs, moles
2. What do soil organisms feed upon?
- Decomposers (e.g., bacteria and fungi) feed on dead plants and animals
- Predators (e.g., protozoa, nematodes) feed on other microorganisms
3. What is decomposition?
- The breakdown of organic matter (dead plants and animals) into simpler forms
4. How do these organisms benefit humans?
- Break down dead things (decomposition)
- Break down and clean up pollutants in the environment
- Provide nutrients to plants, protect plants from diseases, and aerate the soil, all which helps crops to grow
- Help structure the soil with their “glue”, preventing erosion
Suggested Activities and Curriculum Connections:
- Learn more about the types of organisms in soil with Grady the Tardigrade and the Sci Show Kids team: Soil is Alive!
- Isolate organisms from soil so you can view them under a microscope using a Berlese Funnel
- Watch some soil organisms under the microscope: Soil Biology Movies contains 16 movies of organisms living in soil. Or watch a video of a soil sample under the microscope.
- Soil Your Undies to determine how active your soil decomposers are.
- Put those decomposers to work to turn kitchen scraps into nutrient rich compost for your garden! Build a composter in the school yard or a worm bin in your classroom.
- Demonstrate the importance of soil organisms and their “glues” for giving soil structure and preventing erosion.
