The mutualisms between plants and other organisms in the soil revolve around soil nutrients. Soils are the source of almost all mineral nutrients, and the bacteria (root nodules) and fungi (mycorrhizae) in soil help plants to obtain these nutrients in return for aid from the plants (carbohydrates). Organisms from those two groups along with those from the animals (such as earthworms) consume dead matters in the soil, helping to resolubilize nutrients and provide organic humus which improves various properties of the soil.
Work Step by Step
Skim the chapter and make a list (especially from Concept 37.1) of instances in which non-plants have an important role in the soil/soil nutrition. Use this list to construct your answer, which is a kind of summary of the chapter.