Which of the following is a characteristic of obligate symbiosis?

Obligate symbiosis is a type of symbiotic relationship where two species have evolved to be so dependent on each other that they cannot survive without one another. In this context, the correct answer emphasizes that organisms involved in obligate symbiosis rely entirely on each other for their existence, making their interactions crucial for their survival.

For example, a classic instance of obligate symbiosis can be observed in certain species of ants and aphids, where ants protect aphids from predators in exchange for honeydew, a sugar-rich fluid produced by aphids. In this relationship, both species have developed adaptations that ensure their survival is intricately linked.

In contrast, other types of symbiotic relationships might allow one or both species to survive independently, as seen in facultative symbiosis, where species can still thrive without the other. Mutual benefit can sometimes exist in obligate relationships, but it is not the defining feature, as the emphasis is on the dependency rather than mutual benefits alone. Lastly, temporal associations are characteristic of relationships that are not obligate, as they suggest that the organisms interact for only a limited period, contradicting the essence of obligate symbiosis.