Plants and animals play an important role in the development of soils. A. Small organisms such as bacteria and fungi create and enrich soils by breaking down rocks and organic matter. B. Prairie and tundra soils can be found in areas where conditions are generally not favorable for soil development. C. Such agricultural crops as alfalfa, clover, soybeans, peas, and peanuts provide nutrient minerals to the soil as they die and decompose. D. Certain animals block soil development by digging holes in the ground that prevent nutrients from reaching some areas of the soil. E. Trees and other large plants aid soil development by providing natural fertilizer as they decompose, and by protecting the soil against erosion. F. Protozoa, earthworms, and small mammals contribute to soil development by aerating, fertilizing, and mixing the soil.