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The Dirt on Soil Down & Dirty Field Guide Soil Safari

Amoeba Amoeba
Amoeba proteus

Vital Statistics:
Length:0.3 mm (40 would fit between the lines on your notebook paper).
Lifespan:Can survive long inactive periods in dry, sealed capsule.
Total Protozoa Population:up to 10 billion per square meter (5 million in one teaspoon of soil).

Natural History:
Soil amoebas belong to a diverse group of one-celled animals called protozoa. They roam the film of water coating each soil particle. This water layer is so thin that an amoeba can still survive in even very dry soils.

An amoeba uses its blobby tentacles both to move and to feed. It doesn't waste any time chewing its food. Its tentacles surround a food item and bring it inside its body. A single amoeba can eat thousands of bacteria each day. Amoebas eat so many bacteria that they compete with nematodes for food. Soils with lots of protozoa have fewer nematodes.

Amoebas belong to the soil recycling crew. They can't use all of the nutrients in the bacteria they eat. So a lot of the nutrients go back into the soil. Plants use these nutrients to grow.

Amoebas and other protozoa must breath oxygen. They mostly live in the top layer of soils that mix well with the air.

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Pictures: Saskatchewan Interactive/Dr. Jeff Bettany | Point Pelee National Park, Canada |
Yuuji Tsukii

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