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Suggest that students make a poster display showing the web of living things that they found in their soil samples and how they think these are related to one another. To do this, they will need to find more information about the various types of life found in the soil community. You might assign research topics to each group, e.g. “Find out what kinds of insects live in the soil and what they do for the soil community.”
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© BLM |
Sample Soil Organism Web |
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Soil organisms come in all shapes and sizes—microscopic forms include varieties of bacteria, fungi, algae, and protozoa; macroscopic forms include insects, worms, and even burrowing mammals and reptiles. Students will be surprised to hear that there are many more living things in the soil than those they found while examining their samples. In fact, healthy soil is loaded with life. One estimate is that a hectare of soil supports about 20,000 kilograms of living things, approximately equal to the weight of 40 horses. (Non-living organic matter is present at about 20 times this amount!)
But if we can’t see these living things, how do we know they are there? In fact, their presence can be detected by many of the clues they leave behind as they go about their activities. Like nearly all living things, soil organisms provide an important chemical clue that they are alive and breathing. They exhale or simply give off the chemical carbon dioxide—a chemical that is easily detected in water by use of an indicator. The more carbon dioxide present, the more living things are present in the soil.
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