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The Story of Soil

When bedrock is broken down into small rock pieces, fungisoiltunnelsrootsSelect your answer starts to form. The breakdown is caused mostly by rain, ice, wind, freezing and thawing, or fungihumuschemicalbacteriaSelect your answer changes. Plant rootssoilbacteriafungiSelect your answer spreading downward break these pieces apart further. Some burrowing animals make humusrootstunnelsbacteriaSelect your answer that fill with air and water. This water expands as it freezesfungirootstunnelsSelect your answer, causing more breakdown. Dead animals and plants are decomposed by humusbacteriafreezeschemicalSelect your answer and chemicalfungisoilrootsSelect your answer for energy. The leftover decomposed plants and animals, called humusfungisoilbacteriaSelect your answer, mix with the rock pieces forming soil.