Two species benefit from interaction with each other

Example: A hummingbird gets food from the nectar of a flower and then spreads the nectar’s pollen, helping the flower reproduce.


: One species benefits from the interaction, and the other species is harmed but not necessarily killed

Example: Ticks feed on other animals’ blood, which can hurt the other animals.


: One species benefits from the interaction, and the other species is neither helped nor harmed

Example: Egrets rely on cows to stir up dirt and bring food to the surface, but cows do not benefit.