What ecological principle can be gleaned from the relationship between algae and sloths?

In the relationship between algae and sloths, the principle of commensalism is illustrated. In this type of ecological interaction, one species benefits while the other is neither helped nor harmed. In this case, algae grow on the fur of sloths. The algae benefit by gaining a habitat and access to the sunlight they need for photosynthesis. Meanwhile, the sloths do not gain any direct benefit or detriment from the presence of the algae; their health and survival are not significantly impacted by the algae growing on them. This interaction exemplifies commensalism perfectly, showcasing how one organism can thrive while the other remains unaffected.

In contrast, competition would involve both organisms seeking the same resources, potentially causing harm to both, while mutualism would imply benefits to both parties involved. Parasitism would mean one organism benefits at the expense of the other, which is also not the case here. Hence, the relationship between algae and sloths clearly aligns with the definition of commensalism.