The sign + is used to indicate an association where an organism gains, while 0 is used where an organism is unaffected. An association indicated as +0 is kn...

An association indicated as +0 is known as commensalism. Commensalism is a type of symbiotic relationship between two organisms where one organism benefits while the other is neither helped nor harmed. In the given context, the plus sign (+) indicates that one organism benefits from the association, while the zero (0) indicates that the other organism is unaffected. Therefore, in a +0 association, one organism benefits, while the other is neither helped nor harmed. Examples of commensalism in nature include certain species of fish that follow larger animals such as whales or sharks, feeding on the leftovers from their meals without harming them. Similarly, some species of birds build their nests in the trees of other birds, using the existing structure without affecting the host bird's ability to use the nest. Therefore, an association indicated as +0 is known as commensalism, which is a type of symbiotic relationship where one organism benefits while the other is unaffected.