Distinguish among symbiosis, obligate, and facultative mutualism.

Symbiosis is a close, long-lasting interaction between two different species. It can occur in various forms such as mutualism, commensalism, or parasitism. In a symbiotic relationship, at least one of the species benefits, and it may or may not harm or provide any benefit to the other species involved. Symbiosis is an important part of ecology, as it helps in maintaining the balance in ecosystems.

Obligate mutualism is a type of symbiotic relationship in which both species are dependent on each other for survival and reproduction. In this relationship, both species benefit, and their interaction is essential for their existence. One classic example of obligate mutualism is the relationship between pollinators (such as bees, butterflies, or birds) and flowering plants. The pollinators get food from the plants (in the form of nectar), and in return, they facilitate the reproduction of plants by transferring pollen from one flower to another.

Facultative mutualism is a type of symbiotic relationship in which both species benefit from their interaction, but their association is not essential for their survival and reproduction. In other words, they can live independently without the help of their partner species but may enjoy some advantages when they do interact. An example of facultative mutualism is the relationship between certain species of ants and aphids. The ants protect aphids from their predators, and in return, the aphids provide a sugary substance called honeydew for the ants to feed on. However, both species can survive without each other. In summary, symbiosis is a close interaction between two different species, which can take different forms, such as mutualism. Obligate mutualism is a type of mutualism where both species are dependent on each other for survival, while facultative mutualism is a type of mutualism where the association is beneficial but not essential for the survival of both species.