Which scenario best illustrates a mutualistic relationship?

Which scenario best illustrates a mutualistic relationship?

• A. E. coli in the human gut aiding digestion
• B. Ruminococcus species using nutrients from a cow's diet to digest plant cellulose in the rumen
• C. A virus infecting a healthy cell
• D. Parasitic worms in a host causing disease

Answer: (B)

The scenario that best illustrates a mutualistic relationship is that of Ruminococcus species using nutrients from a cow's diet to digest plant cellulose in the rumen. In this relationship, both the Ruminococcus bacteria and the cow benefit from their interactions. The cow provides the bacteria with a suitable environment and nutrients found in its diet, and in turn, the bacteria help break down cellulose, a complex carbohydrate found in plant material, which the cow is unable to digest on its own. This mutualistic relationship enhances the cow's ability to extract energy and nutrients from its diet while also providing the bacteria with a habitat and food source. Overall, both organisms gain advantages from this interaction, which is the hallmark of mutualism.