Interspecific (between individuals of different species)
Association between individuals that may be mandatory (symbiosis) or optional (protocooperation).
In the obligatory association, both individuals benefit, but each species can only live in the presence of the other. Eg lichen, oxen and microorganisms of the digestive system.
Bees, hummingbirds and butterflies are some animals that feed on flower nectar. Nectar is produced at the base of flower petals and is a product rich in sugars. When bees, butterflies and hummingbirds gather nectar, pollen grains are deposited on their body. Pollen contains male reproductive cells of the plant.
Perching on another flower, these insects drop pollen on the female part of the plant. The two reproductive cells - male and female - will then unite and give rise to the embryo (contained within the seed). Note that there is a relationship between these insects and the plant on which they both profit. This kind of relationship between two different species and one that benefits both is called mutualism.
Pollinating animals get food and the plant reproduces itself.
Another example is lichens, a mutualistic association between algae and fungi. Fungi protect algae and provide them with water, minerals and carbon dioxide, which they remove from the environment. Algae, in turn, photosynthesize and thus produce part of the food consumed by the fungi.
Lichens and Pollinators