Aparticular plant species is pollinated by a certain insect species. the insect species depends on the plant species for food. which term describes how this relationship forms?

reproductive isolation

co-adaptation

mass extinction

instantaneous speciation

A particular plant species is pollinated by a certain insect species. The insect species depends on the plant species for food. This relationship is based on co-adaptation.  

Here co-adaptation refers to the mutual adaptation between the given species(plants and insects) that depend upon each other.